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