Block 2 Flashcards
Why is water wet?
Its a liquid due to its hydrogen bonding
What are 3 different intermolecular forces?
(London) dispersion forces, Van der Waals, Hydrogen bonding.
What are (London) dispersion forces?
The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles.
What are Van der Waals forces?
A distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules.
What is hydrogen bonding?
A hydrogen bond is a partial intermolecular bonding interaction between a lone pair on an electron rich donor atom, particularly the second-row elements nitrogen, oxygen, or fluorine, and the antibonding orbital of a bond between hydrogen and a more electronegative atom or group.
What are electrostatic interactions?
Electrostatic interaction (van der Waals interaction): The attractive or repulsive interaction between objects having electric charges.
What are temporary dipoles?
Temporary dipoles are created when electrons, which are in constant movement around the nucleus, spontaneously come into close proximity. This uneven distribution of electrons can make one side of the atom more negatively charged than the other, thus creating a temporary dipole, even on a non-polar molecule.
What are permanent dipoles?
Permanent dipoles. These occur when two atoms in a molecule have substantially different electronegativity: One atom attracts electrons more than another, becoming more negative, while the other atom becomes more positive. A molecule with a permanent dipole moment is called a polar molecule.
Temperature is directly proportional to…?
The average speed (Kinetic energy) of all the particles in the material.
Changing a liquid to a gas is referred to as the…?
The enthalpy of vaporisation
What is enthalpy?
Enthalpy, a property of a thermodynamic system, is equal to the system’s internal energy plus the product of its pressure and volume
What is a non-polar molecule?
A molecule that is symmetrical and/or has no difference in electronegativity within its bonds.
What is a polar molecule?
A molecule that is non-symmetrical and has a difference in electronegativity within its bonds.
True or False? Hydrogen bonds have to be overcome before the water molecules can move faster and the temperature can increase.
True
How come metals can conduct electricity?
Metals conduct electricity because the electrons inside the metal are relatively free to move. So when electricity is through metals, electrons carry electricity and spread it all over the metal. The mobility of electrons is the reason why metals conduct electricity.
What is a solution?
A solution must be clear.
What is a solution?
Tiny particles of solute dispersed in a solvent. A solution must be clear.
What is an emulsion?
An emulsion is a mixture of two or more liquids that are normally immiscible (Cant be mixed or blended together)
What is a suspension?
In chemistry, a suspension is a heterogeneous mixture that contains solid particles sufficiently large for sedimentation
What are adhesive properties?
Adhesion is the ability of dissimilar molecules to stick together.
What are cohesive properties?
Cohesion is the ability of like molecules to stick together. Water is strongly cohesive
What is a Solvent?
The ‘thing’ that does the dissolving. (The larger amount)
What is a Solute?
The ‘thing’ that gets dissolved. Solids, liquids and gases can be dissolved. (The smaller amount)
What determines the strength of an ionic lattice?
How close the atoms are together.
What is surface tension?
Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area possible. Surface tension allows insects, usually denser than water, to float and slide on a water surface.
What does solubility depend on?
The term “Like dissolves in Like”-
What does Entropy mean?
It is a movement towards disorder. It states that systems will tend to favour disorder as it is a less energetic situation.
To oppose entropy would you require high energy or low energy emmisions?
High energy emmisions.
What is the meniscus?
The meniscus is the curve seen at the top of a liquid in response to its container. … Most liquids, including water, present a concave meniscus
What are saturated solutions?
A saturated solution is one in which the maximum amount of a solute is dissolved for that particular temperature.
What is the saturation point?
The point at which no more solute will dissolve no matter how long you wait.
What is dynamic equilibrium?
A dynamic equilibrium is a chemical equilibrium between a forward reaction and the reverse reaction where the rate of the reactions are equal
Why does Ice Float?
Ice floats on water because it is less dense than water. When water freezes into its solid form, its molecules are able to form more stable hydrogen bonds locking them into positions.
What does pressure do to ice?
It melts it.
True or False? Water can bank heat
True
What are bond enthalpies?
Bond enthalpy (also known as bond energy) is defined as the amount of energy required to break one mole of the stated bond.
What is precipitation?
Precipitation is the creation of a solid from a solution. When the reaction occurs in a liquid solution, the solid formed is called the ‘precipitate’. The chemical that causes the solid to form is called the ‘precipitant’.
What is hydration?
Interaction of a substance with water
What does saturated mean?
containing the greatest possible number of hydrogen atoms, without carbon–carbon double or triple bonds.
What is equilibria?
a state in which opposing forces or influences are balanced.
What is a solubility product?
A solubility product, or Ksp, is the equilibrium constant for a chemical reaction in which a solid ionic compound dissolves to yield its ions in solution
What is ion association?
Ion association is a chemical reaction whereby ions of opposite electrical charge come together in solution to form a distinct chemical entity.
What are soluble salts?
Soluble salts are the compounds which readily dissolve in water.
What are Insoluble salts?
Insoluble salts are ionic compounds that are insoluble in water: the salt continues to exist as a solid rather than dissolving in the liquid
What are compound ions?
A compound that will ONLY lose or gain electrons
What does monoatomic mean?
It means to consist of only 1 atom.
Why does water appear blue when deeper than a few centimetres?
The blue hue of water is an intrinsic property and is caused by selective absorption and scattering of white light.
What is surface tension?
It is where the H2O molecules at the surface of the water are attracted to each other but repulse away from air as the water molecules are very polar and the air molecules are very non-polar.
What direction does the molecular dipole go in?
Towards the positively charged atom.
What is the equilibrium constant (K)?
The equilibrium constant is an equation that can help us understand whether the reaction tends to have a higher concentration of products or reactants at equilibrium.
What is a reversible reaction?
A reversible reaction is a reaction that can proceed in both the forward and backward directions.
True or False? Equilibrium is a state of balance.
True
What is dynamic equilibrium?
In chemistry, and in physics, a dynamic equilibrium exists once a reversible reaction occurs. Substances transition between the reactants and products at equal rates, meaning there is no net change
True or False? During dynamic equilibrium more products are being produced.
False, during dynamic equilibrium it appears nothing is happening as both products and reactants are produced at equal rates.
What is the equilibrium constant expression?
K = [C]c [D]d / [A]a [B]b
In chemistry what do brackets mean [ ] ?
Concentration
What states are included in the equilibrium constant expression?
Gaseous and Aqueous states.
Are solids pure solvents?
Yes.
Are solids included in the equilibrium constant expression?
No, they are left out because they have an activity of 1.
What is the thermodynamic equilibrium constant?
Defined to be the value of the reaction quotient Qt when forward and reverse reactions occur at the same rate
What is the reaction quotient Qt?
The reaction quotient (Q) measures the relative amounts of products and reactants present during a reaction at a particular point in time
What happens to equilibrium when you change the temperature?
Equilibrium changes
What does it mean if Q=K? (The reaction quotient = the equilibrium constant expression)
The system is at equilibrium
What does the subscript (o) stand for?
Initial concentration
If your value is above 10^3, are you producing more reactants or products?
Products
What does (te) stand for?
Time at equilibrium
What does Qc stand for?
The ratio of the concentrations or partial pressures of a system at a specific point at which the forward and reverse reactions are occurring. It has not yet reached equilibrium, so it will be different from K
What is Le Chateliers principle?
If a system at equilibrium is disturbed, the system tends to shift its equilibrium position to counter the effect of the disturbance.
Who is Henri Le Chatelier?
He studied mining engineering and was interested in glass and ceramics. He discovered Le Chateliers principle of equilibirum.
If a system at equilibrium experiences a concentration change what happens?
They is no change to K only to the equilibrium composition.
What causes pressure in a chemical system?
Pressure is caused by gas molecules hitting the sides of their container. The more molecules in the container, the higher the pressure will be
If volume decreases what happens to pressure?
Pressure increases
What is volume?
The amount of space that a substance or object occupies, or that is enclosed within a container.
What is a chemical catalyst?
A catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction
What does a chemical catalyst do to a system at equilibirum?
It does not change K, but it does change the rate at which equilibrium occurs or is achieved.
What does exothermic mean?
(of a compound) formed from its constituent elements with a net release of heat.
What does endothermic mean?
An endothermic process is any process which requires or absorbs energy from its surroundings
If delta H is + is the reaction endothermic or exothermic?
Endothermic
If delta H is - is the reaction endothermic or exothermic?
Exothermic
What does a temperature change do to a system at equilibrium?
It changes the value of K.
What changes to a system at equilibrium do not change the value of K?
Changes to: Concentration, pressure, and the addition of a catalyst.
What change to a system at equilibrium change the value of K?
Changes to temperature.
When evaluation the effect of a change to a system at equilibrium, what formula should you use?
Change, effect, response, and result.
Do exothermic reactions break or make bonds?
Bond Making
Do endothermic reactions break or make bonds?
Bond Breaking
What is the general equation for exothermic reactions?
Reactants → Products + Energy
What is the general equation for endothermic reactions?
Reactants + Energy → Products
What does +ve mean?
Positive
When solving problems to do with chemical equations what ratios does everything NEED to be in?
Mole ratios
For the kc equation, do products go over reactants, or reactants over products?
Kc = Products/Reactants.
What are some of the properties of acids?
They taste sour, they are corrosive, they turn blue litmus red, and they have a pH less than 7 at 25 degrees.
What are some properties of bases?
They taste bitter, they can be corrosive, they turn red litmus blue, and they have a pH greater than 7 at 25 degrees.
If you temperature does pH change?
Yes!!
What are some common examples of acids?
Hydrochloric acid (HCl) in gastric juice. Sulphuric acid (H2SO4) Nitric acid (HNO3) Carbonic acid in soft drink (H2CO3)
What are some common examples of bases?
Potassium hydroxide (KOH) Sodium hydroxide (NaOH) Barium hydroxide (Ba(OH)2) Caesium hydroxide (CsOH) Strontium hydroxide (Sr(OH)2) Calcium hydroxide (Ca(OH)2)
Acids change the colour of what?
Indicators
Acids react with certain metals to give what?
A salt and a hydrogen
Acids react with carbonate to give what?
A salt and water. and carbon dioxide.
Acids react with bases to give what?
a Salt + water
Bases are what type of metals?
Oxides and hydroxide metals that are mostly insoluble in water
What is a base called that is soluble in water?
An alkali
What are alkalis?
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal chemical element. An alkali also can be defined as a base that dissolves in water.
What do alkalis change the colour of?
Indicators reversing the changes produced by acids
Alkalis react with many salt solutions to form what?
Precipitates of insoluble hydroxides.
Alkalis react with ammonium salts to give what?
Precipitates of insoluble hydroxides
Alkalis react with acids to form what?
Salt and water.
What is the general definition of an acid?
Hydrogen ion donators
What is the general definition of an base?
Hydrogen ion acceptors
Who is Suante Arrhenius?
A swedish scientist 1859-1927 who gave his own definition and view of what acids and bases are.
What is suante arrhenius’s view on what acids are?
Substances that give hydrogen in solution.
What is suante arrhenius’s view on what alkalis are?
Substances that give hydroxide ions in solution
What is the acid-alkali reaction?
The reaction between any acid and alkalis in which the only reaction product is the same (Water H2O)
What are neutralisation reactions?
In chemistry, neutralization or neutralisation is a chemical reaction in which an acid and a base react quantitatively with each other. In a reaction in water, neutralization results in there being no excess of hydrogen or hydroxide ions present in the solution.
What are hydrogen halides?
Hydrogen halides are diatomic inorganic compounds with the formula HX where X is one of the halogens: fluorine, chlorine, bromine, iodine, or astatine. Hydrogen halides are gases that dissolve in water to give acids which are commonly known as hydrohalic acids
What bond would occur with an electronegativity difference of 0.0-0.4?
Non-polar covalent bond
What bond would occur with an electronegativity difference of 0.4-1.9?
Polar covalent bond
What bond would occur with an electronegativity difference of 2.0 and above?
Ionic covalent bond
Define electronegativity.
A measure of an atoms ability to attract a pair of electrons in a bond.
Who are Johannes Nicolaus Bronsted and Thomas Martian Lowrry?
Both are scientists that came up with very similar ideas about acids and bases and funnily the same time.
What are conjugate acids?
the species that donates a hydrogen cation or proton in a reaction is a conjugate acid.
What are conjugate bases?
the one that accepts a proton or hydrogen is the conjugate base.
What does conjugate mean?
coupled, connected, or related.
What are spectator ions?
Spectator ions are ions that are present in a solution but don’t take part in a solution’s chemical reaction. When reactants dissociate into ions, some of the ions may combine to form a new compound. The other ions don’t take part in this chemical reaction and are therefore called spectator ions.
What is a monoprotic acid?
A monoprotic acid donates only one proton or hydrogen atom per molecule to an aqueous solution. This is in contrast to acids capable of donating more than one proton/hydrogen, which are called polyprotic acids
What does amphiprotic mean?
By definition, something that is amphiprotic is a molecule (or compound) that can both donate and accept a proton. … Amphoteric refers to substances that can act as either an acid or base.
Fill in the blanks, The stronger the acid the … the ….
The stronger the acid the weaker the conjugate base
Fill in the blanks, The stronger the base the … the ….
The stronger the base the weaker the conjugate acid
What is the hydrocarbonate ion (HCO3-) associated with?
Bicarbonate serves a crucial biochemical role in the physiological pH buffering system. It is amphiprotic and can be both an acid and a base. Acid - H2CO3 Base - CO3^2-
What are buffering systems?
A buffer is simply a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffers work by reacting with any added acid or base to control the pH.
What are the difference between strong vs weak acids and bases?
The difference between strong and weak acids and bases is the degree of ionisation. As strong acids and bases are able to completely dissociate and weaker acids and bases can only partially dissociate leading to equilibrium systems.
Is water an acid or a base?
Water is amphiprotic therefore it can be both.
What are the generic ways to show weak acids and weak bases reacting with equilibrium?
HA + H2O (Double arrow) H30+ + A-
What does HX mean?
HX stands for Hydrogen Halogen, for example HCl, Hbr, HI.
What is Ka?
Kₐ, is a quantitative measure of the strength of an acid in solution. K stands for equilibrium constant and a stands for the acidity constant.
What does the strength of an acid or base depend on?
The number of ions it produces in solution
What is acidity a measure of?
A measure of strength
What does HA stand for?
The HA is the acid
What does A- stand for?
A- is the conjugate base
What are some common bases?
NaOH (Sodium Hydroxide), LiOH (Lithium hydroxide), KOH (Potassium hydroxide), NH3 (Ammonia)
What are some common acids?
HNO3 (Nitric acid), HCl (Hydrochloric acid), HCN (Hydrogen cyanide), HCOOH (Formic acid)
What is p-notation?
The p-scale is a negative logarithmic scale. It allows numbers with very small units of magnitude (for instance, the concentration of H+ in solution) to be converted into more convenient numbers
What is the pH scale?
In chemistry, pH is a scale used to specify how acidic or basic a water-based solution is. It is based of potenz hydrogen
How do you calculate pH?
pH = -log^10 [H3O+]
How do you calculate [H3O+] from pH?
[H3O+] = 10^-pH
Fill in the blanks. The more H+ ions the ? the power of 10, therefore, the ? the pH number.
The more H+ ions the smaller the power of 10, therefore, the smaller the pH number.
If the H30+ conc is 1x10^-4 what would the pH be?
4
If the H30+ conc is 1x10^-8 what would the pH be?
8
If the H30+ conc is 1x10^-2 what would the pH be?
2
If the H30+ conc is 1x10^-1 what would the pH be?
1
If the H30+ conc is 1x10^-12 what would the pH be?
12
What is the pH of HCl at 25 degrees?
1
What is the pH of HCOOH at 25 degrees?
2.38
What is the pH of HNO3 at 25 degrees?
1
What is the pH of HCN at 25 degrees?
5.15
What would happen if your bodys pH levels went higher than 7.45?
Respiratory or metabolic alkalosis which if not treated causes death.
What would happen if your bodys pH levels went lower than 7.35?
Respiratory or metabolic acidosis which if not treated causes death.
What is molality?
a measure of the concentration of a solute in a solution in terms of amount of substance in a specified amount of mass of the solvent.
What is the pOH scale?
pOH is a measure of hydroxide ion (OH-) concentration. It is used to express the alkalinity of a solution. Opposite to the pH scale.
What are monoprotic acids?
A monoprotic acid donates only one proton or hydrogen atom per molecule to an aqueous solution.
Are most acids weak acids or strong acids?
Weak acids
What are most strong acids?
Inorganic acids
What are quadratic equations?
In algebra, a quadratic equation is any equation that can be rearranged in standard form as where x represents an unknown, and a, b, and c represent known numbers, where a ≠ 0. ax^2+bx+c=0
What are the 2 assumptions of conjugate acid and base reactions?
- At equilibrium [H3O+] = [A-]
2. That the amount of HA at equilibrium is equal to the amount of HA initially put in (Because so little dissociates)
What is the log scale?
A logarithmic scale is a way of displaying numerical data over a very wide range of values in a compact way
What is Kb?
Kb is the base dissociation constant. The base dissociation constant is a measure of how completely a base dissociates into its component ions in water
What is Kw?
the dissociation constant or ionization constant of water
Strength is related to the what of an acid?
The degree of ionisation of the acid
What is pka?
The pKa is the pH value at which a chemical species will accept or donate a proton. The lower the pKa, the stronger the acid and the greater the ability to donate a proton in aqueous solution.
Lower pH means greater the concentration of what?
H+ Ions
What are titration curves?
Titrations are often recorded on graphs called titration curves, which generally contain the volume of the titrant as the independent variable and the pH of the solution as the dependent variable.
What is the equivalent point?
When the acid is entirely neutralised
What is the end point
When the indicator colour changes.
What does the first point on a titration point show you?
Whether you are dealing with a strong or weak acid or base?
What is the neutralisation point?
The neutralisation point is that amount of titrant added where there is nothing in the solution but salt (the neutralisation reaction is complete)
What is the 1/2 neutralisation point?
In the middle of this gradually curve the half-neutralisation occurs. At this point the
At the 1/2 neutralisation point pH = what?
The pka of the acid
What is the buffer region?
The buffering region is about 1 pH unit on either side of the pKa of the conjugate acid. A titration curve visually demonstrates buffer capacity,
What are acid base indicators?
Acid - Base indicators (also known as pH indicators) are substances which change colour with pH. They are usually weak acids or bases, which when dissolved in water dissociate slightly and form ions. Consider an indicator which is a weak acid, with the formula HIn or ln-
What is phenolphthalein?
Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions
What is litmus?
a dye obtained from certain lichens that is red under acid conditions and blue under alkaline conditions
What is bromothymol blue?
BMB is blue when the pH is greater than 7.6, green when the pH is between 6-7.6, and yellow when the pH is less than 6.
What is methyl red?
Methyl red also called C.I. Acid Red 2, is an indicator dye that turns red in acidic solutions.
What is methyl violet?
It is used as a pH indicator, with a range between 0 and 1.6. The protonated form (found in acidic conditions) is yellow, turning blue-violet above pH levels of 1.6.
What is methyl orange?
Methyl orange shows red color in acidic medium and yellow color in basic medium
What is thymol blue?
A pH indicator that transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6.
When does the indicator change colour in a titrant?
When the quantity of added titrant is the exact amount necessary for the reaction.
What is a buffer solution?
A buffer solution is a solution which has the capacity to maintain an almost constant pH when small amounts of strong acid or strong base are added
What is the henderson hasselbalch equation?
In chemistry and biochemistry, the Henderson–Hasselbalch equation can be used to estimate the pH of a buffer solution if the value of the acid dissociation constant, Kₐ, of the acid is known or assumed. pH = pK_a + log10([A^-] / [HA])
What is the blood buffer system?
When any acidic substance enters the bloodstream, the bicarbonate ions neutralize the hydronium ions forming carbonic acid and water. … On the other hand, when a basic substance enters the bloodstream, carbonic acid reacts with the hydroxide ions producing bicarbonate ions and water.
What is the fancy name for a red blood cell?
erythrocyte
What is the importance of hydronium ions?
The hydronium ion is an important factor when dealing with chemical reactions that occur in aqueous solutions. Its concentration relative to hydroxide is a direct measure of the pH of a solution. It can be formed when an acid is present in water or simply in pure water.
What is oxidation?
Oxidation occurs when an atom, molecule, or ion loses one or more electrons in a chemical reaction.
What is reduction?
Reduction is a chemical reaction that involves the gaining of electrons by one of the atoms involved in the reaction between two chemicals.
What is redox?
Redox is a type of chemical reaction in which the oxidation states of atoms are changed.
What are oxidation states?
Oxidation state shows the total number of electrons which have been removed from an element (a positive oxidation state) or added to an element (a negative oxidation state) to get to its present state.
What are oxidation numbers?
Oxidation numbers are used by chemists to keep track of electrons within a compound.
What are oxidising agents?
An oxidizing agent (oxidant, oxidizer) is a substance that has the ability to oxidize other substances — in other words to accept their electrons.
What are reducing agents?
An element or compound that loses (or “donates”) an electron to an electron recipient (oxidizing agent) in a redox chemical reaction
How do we know which way the reactions will go in redox?
This has to be determined by experimentation. The results are listed in tables. Written in terms of how strong each substance is as a reductant.
What are reductant potentials?
measures the tendency of a chemical species to acquire electrons and thereby be reduced.
What does LEOs A GERC stand for?
Loss of Electrons is Oxidation, which occurs at the Anode. Gain of Electrons is Reduction, which occurs at the Cathode.
What is a pure element?
In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons.
Following the rules of oxidation numbers, what is the oxidation number of Cl?
O
Following the rules of oxidation numbers, what is the oxidation number of K+?
+1
Following the rules of oxidation numbers, what is the oxidation number of O in CO2 & NO3-?
-2
Following the rules of oxidation numbers, what is the oxidation number of O in hydrogen peroxide and sodium peroxide?
-1
Following the rules of oxidation numbers, what is the oxidation number of O in F2O?
2+
Following the rules of oxidation numbers, what is the oxidation number of H in C2H6?
+1
Following the rules of oxidation numbers, what is the oxidation number of H in LiH?
-1
Are oxidation numbers real?
No they just help us working things out.
What is the criteria for oxidation?
Gain of oxygen, Loss of electrons, Increase in o.n, and a loss of hydrogen.
What is the criteria for reduction?
Loss of oxygen, gain of electrons, decrease in o.n, and a gain of hydrogen.
Are reactants metals or non-metals?
Metals.
Are oxidants metals or non-metals?
Non-metals.
How may valence electrons do reductants usually have?
1 or 2 valence electrons
Do reductants have low or high electronegativity?
Low
What do reductants do?
Donate valence electrons to oxidants therefore forming an ion.
How many valence electrons do oxidants usually have?
5,6 or 7
Do oxidants have high or low electronegativity?
High
What do oxidants do?
Accept electrons from strong reductants and form ions
True or False? Some metals can act as both oxidants and reductants
True
What are redox half reactions?
A half-reaction is simply one which shows either reduction OR oxidation, but not both
What is the KOHES rule?
K stands for Key element
O stands for Oxygen balance by adding H2O
H stands for Hydrogen balance by adding H+ ions
E stands for Electrons, balance by adding e- to the more positive side
S stands for States, add states (e- does not have states)
