Section 1: Principles in Chemistry Flashcards
What are the three states of matter?
The three states of matter are a solid, liquid and gas.
What is the difference in the particles between a solid and a liquid?
What is the difference in the particles between a liquid and a gas?
(forces, position, touching)
A solid has strong forces in between the particles keeping the particles in fixed positions. A liquidhas weak forceswhich allows them to move around but are usually packed closely together.
In a liquid, theparticles are packed closely together but are able to move around. There are weak forces between the particles. Gases are able to freely move around and expand.
Name the 5 state changes and say what happens
Melting - solid to liquid Boiling - liquid to gas Condensing - gas to liquid Freezing - liquid to solid Sublimation - solid to gas
Define diffusion
Diffusion is the movement of particles from a higer concentration to a lower concentration.
Describe the experiment which demonstrates diffusion using ammonia and hydrochloric acid
Cotton wool soaked in aqueous ammonia is placed at one end of a glass tube and at the other end there’s a cotton wool soaked in hydrochloric acid. Eventually, a white ring made up of ammonium chloride will form closest to the hydrochloric soaked cotton wool. The ring is closest to the hydrochloric acid because the ammonia particles are lighter and smaller than they diffuse faster than the hydrochloric acid.
Describe the structure of an atom
The nucleus is in the middle of an atom containing protons and neutrons. Electrons are found outside the nucleus in shells
Name the the three particles found in an atom and state their mass and charge
A protons relative mass is 1 and its relative charge is +1.
A neutrons relative massis 1 and its relative charge is 0.
An electrons relative mass is 1/2000 and its relativecharge is -1.
What does the mass number tell you?
What does the atomic number tell you?
The mass number tells me the total number of protons and neutrons in the atom.
The atomic number tells you the number of protons.
When a small number of atoms are joined together by covalent bonds what do they form?
A molecule
How are molecules held together?
They are held together by covalent bonds.
What is an ion?
When electrons are added or removed from an atom it becomes charged making it an ion.
How do you calculate the relative formula mass?
Ex. How would you find the Mr of MgCl2?
Ex. How would you find the Mr of C2H4(OH)2?
Add up the relative atomic massesof the atoms in the formula
Mg= 24 Cl= 35.5 MgCl2= Mg=24 + Cl2=(35.5x2)=95
C=12 H=1 0=16C2H4(OH)2= (16x2) + (1x4) + [(16+1) x 2] = 62
How can you easily find the Ar of an element?
The mass number on the periodic table
1 What is the mass of one mole of something
2 What do we measure moles in, what is the unit of moles?
3 How much is a mole?(Avagadro’s number of particles)
1 One mole of atoms or molecules of any substance will have a mass in grams equal to the molar mass
2 mol.
3 6.02x10 to the 23rd power
How do you calculate moles from mass?
moles = mass ÷ molar mass
What is the molar volume of gas (the volume 1 mole of gas will occupy)
24dm3or 24,000 cm3
What is the equation for working out the number of moles of a gas?
moles = v (cm3) / 24000
What is a covalent bond?
A covalent bond is formed when two non-metal atoms are combined together by sharing electrons. The positive nuclei of the atoms are attracted to the shared pair of electrons between them, it is a strong attraction
Draw dot-cross diagrams for the following molecules: Hydrogen - H2 Chlorine - Cl2 Hydrogen Chloride - HCl Water - H2O Methane - CH4 Ammonia - NH3 Oxygen - O2 Nitrogen - N2 Carbon Dioxide - CO2 Ethane - C2H6 Ethene - C2H4
Hydrogen atoms can each form one covalent bond. One pair of electrons is shared in a hydrogen molecule (H2)
Chlorine atoms can each form one covalent bond. One pair of electron is shared in a chlorine molecule (Cl2)
Hydrogen and chlorine atoms can each form one covalent bond. One pair of electrons are shared in a hydrogen chlorine atom
Hydrogen atoms can each form one bond, while oxygen atoms can each form two covalent bonds. The oxygen is in the middle with a bond to each hydrogen on either side
Hydrogen atoms can each from one covalent bond, while carbon can form four covalent bonds. A central carbon has four hydrogens bonded around it.
Hydrogen atoms can each form one covalent bond, while nitrogen can form three covalent bonds. A central nitrogen has three hydrogens bonded around it.
Oxygen atoms can each form two covalent bonds. The atoms share four electrons to form a double covalent bond between them
Nitrogen atoms can each from three covalet bonds. The atoms share six electrons to form a triple covalent bond between them.
Oxygen atoms can each form two covalent bonds, while carbon can form four covalent bonds.A central carbon forms a double to an oxygen atom on either side.
Hydrogen atoms can each form one covalent bonds, while carbon atoms can form four covaent bonds. Two carbons are bonded together and then 3 hydrogens are bonded to each carbon.
Hydrogen atoms can each form one covalent bond, while carbon can form four covalent bonds. The two carbons have a double bond between them and then another two hydrogens on each carbon
Why do simple molecular substances have low boiling points?
They have low boiling points because they have weak forcesholding the molecules together which don’t require much energy to overcome
Why do giant covalent structures have high melting points?
The have high melting points because they are in a lattice which has a lot of strong covalent bonds which need to be broken to melt the substance
Draw diamond and graphite in terms of structure
Diamond- Draw one carbon with four others coming off it and continue on the other four
Graphite- Draw carbons in layers, 3 bonds between each atom, weak forces between layers
For the reaction of magnesium and oxygen give the word equation and balanced symbol equation
Magnesium + Oxygen-> Magnesium Oxide
2Mg + O2 -> 2MgO
What do these state symbols represnet?(s), (l), (g), (aq)
(s)-solid (l)-liquid (g)-gas (aq)-aqueous
Can you balance this equation: C3H8 + O2 -> CO2 + H2O ?
`
C3H8 + 5O2 -> 3CO2 + 4H2O
In some salts, water molecules are incorporated in the lattice. What is the water in the lattice called?
Water of crystallisation
When a solid salt contains water of crystallisation, what is it?
Hydrated
When a salt does not contain any water of crystallisation, what is it?
Anhydrous
How can you calculate how much water of crystallisation salt contains?
If you know the mass of the hydrated and anhydrous salt, calculate the number of moles of water lost and anhydrous salt made. Work out the ratio of moles of anhydrous salt to mole of water, the final number must be rounded to a whole number.
What does theempirical formulae work out?
The smallest whole number ratio of atoms in a compound
How do you calculate the empirical formulae?
- Divide each mass or percentage by the relative atomic mas for the particular element. 2. Turn the numbers into a simple ratio by dividing them by the lowest number of those answers.
- Adjust the ratio so all our whole numbers if necessary
What is the molecular formula of a substance
The actual numbers of atoms of each element in a single molecule
How do you calculate the molecular formulae?
The question will give you an empirical formula and a molecular mass. Find the mass of the empirical formula using the atomic masses of the element, divide the molecular mass by the mass of the empirical formula. The molecular formula is the empirical formula multiplied by this number.
What is relative formula mass?
All of the atomic masses of a reactant or product added together.
It is the same as molar mass.
What is theoretical yield?
The yield assuming 100% conversion of reactants to products
How do you calculate the percentage yield?
By dividing the actual yield by the theoretical yeild and then multiplying the answer by 100.Note that it will always be somehwere between 0-100
What happens to the charge of an atom when it:
a. loses an electron
b. gains an electron
a. becomes more positive
b. becomes more negative
What is oxidation and reduction
Oxidation is the loss of electrons
Reduction is the gain of electrons
Describe the changes when sodium and chlorine bond ionically
sodium loses an electron to become a + ion = Na+
Chlorine gains the electron to become a - ion = Cl-
Why do atoms form bonds?
To have a full outer shell to become stable
What is the charge on the following ions (explain how they form)? Mg Br Na O Al N
Mg2+, magnesium has two electrons on it’s outer shell so it loses two electrons to become Mg2+
Br-, bromine has seven electrons on it’s outer shell so it gains one electron to become Br-
Na+, sodium has only one electron on its’s outer shell so only one electron is lost to become Na+
O2-, oxygen has six electrons on its outer shell so gains two electrons to become O2-
Al3+, aluminium has three electrons on its outer shell so loses three to become 3+
N3-, nitrogen has five electrons on its outer shell so gains three to become 3-
Using a dot and cross diagram explain the formation of Sodium Chloride
Sodium (x) has one electron on it’s outer shell while Chlorine(.) has seven, this means that in the diagram chlorine will have an outer shell of 7 dots and 1 cross while the outer shell for Sodium will become 8 Xs
What does the group number and period number of an element tell you?
The group number is the number of electrons on the outer shell. The period number is the number of shells
Name the 4 different type of structures
Giant Ionic lattice
Giant Metallic lattice
Giant Covalent lattice
Simple molecular lattice
What kind of attraction is there between oppositely charged ions and how strong is it?
Electrostatic attraction, which is a very strong attraction
What physical property do ionic compounds have as a result of the strong attraction?
A high boiling and melting point
The structure of a metal is made out of?
Positive ions and a sea of delocalised electrons
Name 5 properties of a metal
High melting/boiling point, shiny, good conductors of heat and electricity, malleable/ductile
What is the attraction that holds metals together
The electrostatic attraction between positive ions and negative delocalised electrons
Why do metals have high melting/boiling points?
Because their bonding is strong
Why are alloys harder than metals
Because the lattice structure is disrupted so the atoms cannot easily move past each other
Why do metals easily conduct electricity?
Because the delocalised electrons can move freely through the structure
What is Electrolysis?
The decomposition of a compound by passing an electric current through it, often to form elements
Negative ions _____ electrons at the positive electrode
Lose
Positive ions _____ electrons at the negative electrode
Gain
What are the rules for predicting the products of electrolysis?
Negative electrode - if reactive metal present in the solution hydrogen gas formed. If unreactive metal present then that is formed instead.
Positive electrode - if a group 7 ion is present in the solution then that element is formed. If not oxygen gas is formed.
What is produced at the anode and the cathode after the electrolysis of: Potassium bromide Silver Bromide Copper Sulphate Copper Chloride
Anode= Bromine, Cathode= Hydrogen Anode = bromine, cathode = silver Anode= copper, cathode = oxygen Anode= copper, cathode = chlorine
What is the overall equation for the electrolysis ofPotassium Nitrate and Potassium Sulphate solutions?
2H2O(l) ——-> 2H2 (g) + O2 (g)
What causes an increase in the amount of metal which is deposited at the negative electrode?
An increase in the current or an increase in the time the current flows for
Why do covalent compounds not conduct electricity?
They have no free moving electrons or ions.
Why can ionic compounds only conduct electricity when molten or in solution?
They can only conduct electricity when their ions are free to move.
Complete the following redox half equation: 2H+ + ___ e- ———-> H2
2(e-)
What happens at the electrodes during the purification of copper by electrolysis?
Impure copper at the anode is oxidised
{ Anode= Cu —–> Cu2+ + 2e- }
Pure copper is produced at the cathode
{ Cathode= Cu2+ + 2e- ——–> Cu }
Define:
element
compound
mixture
element - A substance containing only one type of atom
compound - A substance containing more than one type of atom chemically combined
mixture - A substance containing more than one type of atom not chemically combined
Describe simple distillation
A process which separates a liquid with a lower boiling point from a solution
Describe fractional distillation
A process which separates several liquids from a mixture with similar boiling points
Describe filtration
A process which separates a mixture based on particle size with undissolved solids being unable to fit through the small holes in the filter
Describe crystallisation
A process where a substance with a high boiling point is separated from a solution by allowing the solvent to boil or evaporate away
Describe chromatography
A process where several substances in a mixture are separated by their solubility by allowing a solvent to absorb up a surface (e.g. paper) which the substance are on.
Isotopes
Atoms of the same elements with the same chemical properties but different relative atomic mass. They have the same number of protons but a different number of neutrons
Relative Atomic Mass (Ar)
The average mass of the atoms of an element
when compared to C-12
What is the Periodic Table?
An arrangement of elements in order of atomic number, arranged into groups
Give the electronic configuration for the following elements Hydrogen Lithium Nitrogen Fluorine Sodium Aluminium
H -1 Li - 2,1 N - 2,5 F - 2,7 Na - 2,8,1 Al - 2,8,3
Why is diamond very hard?
Why does diamond not conduct electricity?
Because it has strong covalent bonds throughout the structure which are hard to break
Diamond has no delocalised electrons
Why is graphite used in lubricants?
Why does graphite conduct electricity?
Because it has weak force between the layers, which can be easily broken. The layers are able to slide over each other.
Because carbon atoms only form 3 bonds in graphite there is a left over delocalised electron which can move freely through the structure and conduct electricity.
Define the following terms: Solute Solvent Solution Solubility Saturated
Solute - a substance that can dissolve in a solvent
Solvent - a substance (normally a liquid) that a solute can dissolve into
Solution - the mixture formed by a solute dissolving into a solvent
Solubility - how well something can dissolve in a solvent
Saturated - a solution that has the maximum amount of solute dissolved in the solvent, any additional solute added would remain undissolved
The unit of solubility is often measured in g per 100g of solvent, what does this mean?
The amount in grams of a solute that can dissolve in 100 g of a specific solvent
How is Rf value calculated in chromatography?
The distance travelled by the spot on the paper is divided by the distance the solvent travels is (the solvent front). The answer is always between 0 and 1.
In electrolysis what is:
A cation
An anion
Cation - positive ion
Anion - negative ion
What is the charge on the following ions: Ag Cu Fe Pb Zn OH NH4 CO3 NO3 SO4
Ag+ Cu2+ Fe2+ or Fe3+ Pb2+ Zn2+ OH- NH4+ CO3 2- NO3 - SO4 2-
Fullerenes (C60) as simple molecular forms of carbon where each forms 3 bonds to other carbon atoms. What you would expect in terms of melting point and electrical conductivity
Fullerenes would have low melting point as they are simple molecular with weak forces between the molecules.
As they from only 3 bonds there is a last electron that is delocalised so they conduct electricity well.
