Chemistry Paper 1 (GCSE Edexcel Higher)

How to find the number of neutrons

mass number - atomic number

mass number

the sum of the number of neutrons and protons in an atomic nucleus - relative to isotopes

atomic number

the number of protons in the nucleus of an atom

Isotope

2 or more forms of the same element with equal number of protons but different number of neutrons

Relative Atomic Mass

(Ar) average of the mass number of different isotopes

Relative Atomic Mass equation

(isotope 1 mass no. x percentage abundance of isotope 1) + (isotope 2 mass no. x percentage abundance of isotope 2 / 100% or sum of relative abundance

Q. Boron has 2 isotopes: B-10 and B-11

The relative abundances are 4 and 16

Work out the Ar

(10 x 4 ) + (11 x 16) / (16 + 4) = 10.8

Relative molecular mass (Mr)

The sum of the relative ATOMIC masses (Ar) of the elements in a FORMULA

What did Mendeleev do?

In 1869, arranged 50 known elelemnts based on their properties, left gaps for undiscovered elements and predicted their properties

Features of the modern periodic table

-acending atomic number

- elements in groups (downward collums) have similar chemical properties

- rows (periods) tell you how many shells it has

Difference in ions ending -ate and -ite

-ate = oxygen and 1 other element

-ite = only 1 element

Balance this ionic formula: Ca^2+ NO3-

Ca(NO3)2

Ionic Bonding

Transfer of electrons from a metal to a non-metal

Properites of an Ionic Compound

- Giant Ionic Lattice Structure

- High melting/boiling point

- Only conduct when molten or dissolved

The metal loses electrons in ionic bonding to form a _____________

cation

The non-metal gains electrons in ionic bonding to form an ____________

anion

Structure of Metals

Positive ions in a sea of delocalised electrons, held by strong electrostatic attraction, can conduct

Why metalic bonding is strong

- giant structure

- electrons in outer shell are delocalised

- strong attraction between positive metal ions and negative electrons, holding atoms together

Covalent Bonding

sharing of electrons between nonmetals

Simple Covalent Compound Properties

- Covalent bonding

- Low melting/ boiling point

- Don't conduct

- Gas/ Liquid at room temp

Properties of Giant Covalent Compounds (diamond, graphite etc)

- Giant Covalent Structure

- High melting/ boiling points

- Don't conduct (apart from graphite)/ dissolve

Dot and Cross diagram of methane

Ammonia

NH3

Sulfuric Acid

H2SO4 (Strong Acid)

Alloy

A mixture of two or more metals

How can you show conservation of mass?

A precipitate reaction

Empirical Formula

A formula with the lowest whole-number ratio of elements in a compound

Molecular Formula

A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms eg C6H1206

Q. Compound X has the empirical formula of C2H6N, the Mr of compound X is 88, work out its molecular formula

Mr of EP= 44

88/ 44 = 2

C4H12N2

Moles

amount of particles equal to Avogadro's constant (6.02x10^23)

Mole equation involving avogadro's constant

no. particles = moles x 6.02x10^23

Q. How many atoms in 5 moles of oxygen?

6.02x10^23 x 5 = 3.01x10^24

3.01x10^24 x 2 = 6.02x10^24

Q. How many atoms are there in 3.4 g of ammonia (NH3)? (Ar of N = 14, Ar of H = 1). Assume Avogadro's constant is 6 x 10^23.

Mr = 17

Moles = 3.4/17 = 0.2

Molecules = 0.2 x 6x10^23 = 1.2x10^23

There are 4 atoms in each molecule so

1.2x10^23 x 4 = 4.8 x 10^23

Mole equation involving formula mass

Mass = Mr x Moles

(Massive Mr Mole)

Concentration Equation

Amount = Conc. x Vol

(mol) = (mol/dm3) x (dm3)

25g of CuSo4 is dissolved in 500cm^3 of water. What's the concentration in gdm^-3?

1000cm^3 = 1dm^3 so

500cm^3 = (500/ 1000) = 0.5dm^3

conc = 25/ 0.5 = 50 g dm^-3

Limiting Reactant

A reactant that is totally consumed during a chemical reaction, is directly proportional to the product formed

Caluculating the amount of product formed from a limiting reactant. Q. calcualte mass of aluminium oxide (Al2O3) formed when 135g of aluminium is burned in air

1. balance equation

4Al + 3O2 > 2AL2O3

2. calculate Mr

Al = 27 Al2O3 = 102

3. caluculate moles

(moles = mass/ Mr) = 135/ 27 = 5

4. ratio

4 moles of Al react to make 2 moles of Al2O3

so 5: 2.5

5. calculate mass

2.5 x 102 = 255g

Balancing equations with masses

Q. 54g aluminium react with 216g of iron oxide, forming 102g of aluminium oxide and 168g of iron. Balance the equation.

1. divide mass by Mr for Moles

54/ 27 = 2, 216/(56+16) = 3, 102/(54+48) = 1, 168/12 =3

2. devide by smallest no. moles

2/1 = 2, 3/1 = 3, 1/1 = 1, 3/1 = 3

3. write balanced quation

2Al + 3FeO . Al2O3

Methods to seperate mixtures

- Distillation

- Evapouration

- Filtration

- Fractional Distilation

seperating mixtures

Q. x is a liquid - melting point: 5 degrees, boiling point:60

y is a solid - melting point: 745, boiling point: 1218

y dissolves completely in x

- distil it to get x as y is dissovled completly

- use ctrystallisation to find y

Equation for soluble salt process

sulfuric acid + copper oxide > copper sulfate + water

(acid + metal > salt + water)

soluble things

- all nitrates

- most sulfates (not barium, calc, lead)

- most chlorides (not lead, silver)

- bromides

- sodium carbonate/ hydroxide, ammonium carb/ hydroxide, potassium carb/ hyrdroxie (not any other carbonates or hydroxides)

when can you use filtration

- insoluble solid in liquid

- purification

when can you use crystallisation

- soluble solid in solution

when can you use distillation

- seperating a liquid from a solution

Redox

electron transfer reactions

Rf equation

Distance moved by spot = Rf x Distance moved by substance

Process of sterilizing water

-filtration

- sedimentaition, add iron/ aluminium sulphate to make fine particles clump together at the bottom

- chlorination, chlorine gas kills harmful bacteria

What strong acids do

Fully disociate

6 strong acids

HCl, HBr, HI, HNO3, H2SO4, HClO4

Acid + Base

Salt + water

-Neutralisation reaction

Acid + Metal

salt + hydrogen

Acid + Metal Oxide

salt + water

Acid +metal hydroxide

salt + water

Acid + Metal carbonate

salt + water + carbon dioxide

Acid

any compound that forms H+ ions in solution

Alkali

A base that dissolves in water

Base

substance that reacts with an acid to produce salt and water

methyl orange reactions

red in acid

yellow in neutral

pink in alkaline

Litmus reactions

red in acid

purple in neutral

blue in alkaline

phenolphthalein reactions

colourless in acid

colourless in neutral

pink in alkaline

Electrolysis electrodes

P ositive

A node

N egative

I s

C athode

Electrolysis of copper

- mix impure copper with sulfuric acid to make copper sulfate

- pure copper elctrode (-) and impure copper electrode (+), attatched to eletrical supply, in copper sulfate solution

- positive copper ions from solution and impure electrode (Cu2+) attracted to negative electrode

- gain 2 electrons (+ 2e-) and turn to pure copper

Reactivity series

Please Potassium

Stop Sodium

Calling Calcium

Me Magnesium

A Aluminium

Careless Carbon

Zebra Zinc

Instead Iron

Try Tin

Learing Lead

How Hydrogen

Copper Copper

Saves Silver

Gold Gold

Bioleaching (extracting metals from water)

- add bacteria

- bacteria digest metal ions

- leech out metas

Phytomining (extracting metals from soil)

- plants absorb metal ions from soil

- burn plants

- do electrolysis from ash

Benifits of Recycling

- conserves recources and energy

- protects environment (less landfill)

- saves money

Life Cycle Assessment

Environmental impacts of: energy, materials, products, use, disposal

Le Chatelier's Principle

when a stress is applied to a system in dynamic equilibrium, the system changes in a way that relieves the stress (conteracts change)

Haber process

an industrial process for producing ammonia from nitrogen and hydrogen

Conditions for Haber Process

450 degrees, 200 atm, iron catalyst

Uses of ammonia

fertilisers, explosives, medicines and cleaning products

Properties of transition metals

- middle of periodic table

- hard

- shiny

- malleable

- good conductors

- good catalysts

titration

a measured amount of a solution of unknown concentration is added to a known volume of a second solution (and an indicator) until neutralisation occurs, usually indicated by a colour change

% yield equation

actual yield/theoretical yield x 100

Atom economy equation

Mr of desired product/Mr of all products x100

3 essential elements in fertilisers

nitrogen, phosphorus and potassium

Molar Volume

the volume occupied by 1 mole of a gas at standard temperature and pressure

Molar Volume Equation

molar volume = gas volume/ number of moles

Avogadro's Law of Gases

one mole of any gas always occupies 24dm^3

Mole Equation involving Avogadro's Law of Gases

volume= moles x 24

Fuel Cells

a cell producing an electric current directly from a chemical reaction.

Hydrogen Fuel Cells

- creates electricity chemically by combining hydrogen fuel with oxygen from the air

- more efficent than normal batteries

Fullerenes

Molecules of carbon arranged in hexagons, shaped like closed tubes or hollow balls

Uses of fullerenes

1) To 'cage' other molecules - used to deliver drugs into the body

2) Make good industrial catalysts due to their large surface area

3) Make good lubricants

Nanotubes

- Fullerenes

- Conduct electricity

- Dont break when stretched

- Strengthen materials withought adding weight

Test for Carbon Dioxide

Turns limewater cloudy

Test for Chlorine

Bleaches damp litmus paper