Chemistry Paper 1 - IGCSE edexcel ( triple )

State what is meant by the term isomers

Compounds with the same molecular formula but a different structural/display formula

Give the test for hydrogen gas

Hold a lit splint to the test tube and a squeaky pop will sound.

Explain why the rate of reaction is greatest at the start of the reaction

· Concentration is greatest at the start

· More frequent collisions

Explain in terms of the particle collision theory how increasing the temperature affects the rate of reaction

-Particles gain more kinetic energy.

-More collisions have energy greater than the activation energy/more collisions are successful.

-Rate of reaction increases

State what is meant by the term isotope

- Atoms of the same elements with the same number of protons

-but a different number of neutrons.

(This is a water of crystallization question) if the actual value of X was five. - give a reason why the calculated value of X is lower than the actual value.

Not all the water is removed

Discuss the differences between diamond and graphite(6)

-diamond has a tetrahedral structure

-graphite has a hexagonal structure

-diamond does not conduct electricity, but graphite does

-diamond has no delocalised electrons, but graphite does

-Diamond is hard, graphite is soft

-Graphite has layers that can slide over each other

Explain why C60 fullerene a much lower melting point than diamond and graphite.

-C60 fullerene has weak intermolecular forces

-little energy is needed to overcome these forces

-Diamond and graphite have many strong covalent bonds

-so a large amount of energy is needed to overcome the covalent bonds.

What is the charge on PbO?

2+

Explain why the reaction of yellow lead oxide with hydrogen gas is a redox reaction

Lead oxide loses oxygen so is reduced

Hydrogen gains oxygen so is oxidised

Describe a physical test to show that the water produced in this reaction is pure.

Measure the boiling point of the water and the boiling point is 100°c

Describe what the scientist should do next to make sure that all the red lead oxide has reacted

-Heat crucible

-Repeat until a constant mass is obtained

Write down the formula for ammonium carbonate

(NH4)2CO3

Describe a test for ammonium ions

Test the gas for damp red litmus paper

The red litmus paper turns blue

Fertilizer add nitrogen to the soil to help plants grow.

Ammonia and ammonium sulfate can be used as fertilisers.

Discuss the advantages and disadvantages of using each of these compounds as fertilizers.(4)

-Ammonium sulfate is easy to use and easy for the plants to absorb

-Ammonium sulfates pH close to that of rainwater so will not alter the pH of the soil

-Ammonia will cause the soil/water to become alkaline which may kill the plants.

-Ammonia and ammonium is soluble so runoff leads to eutrophication.

Ethane and ethene both react with bromine.

Describe the differences in the reactions of ethane and ethene with bromine

Referred to the conditions , the products and the types of reactions involved.

-Ethane needs UV radiation to react

-ethane produces bromoethane

-ethane reaction is substitution

-ethene produces dibromoethane

-Ethene reaction is addition.

understand ionic bonding in terms of electrostatic attractions

• A giant structure of ions Held together by strong electrostatic forces of attraction between oppositely charged ions

understand why compounds with giant ionic lattices have high melting and boiling points

Strong electrostatic forces of attraction between oppositely charged ions Requires lot of energy to overcome these forces of attraction Therefore the compounds have high melting and boiling points

know that ionic compounds do not conduct electricity when solid but do conduct electricity when molten and in aqueous solution

As a solid , the ions are in fixed positions so can't conduct electricity when molten or in aqueous solution the ions are free to move carrying charge and conducting electricity

describe tests for hydrogen

Creates a ' squeaky pop sound Use a burning splint held at the open end of a test tube of the gas

test for oxygen

Uses glowing splint inserted into a test tube of the gas Splint relights in oxygen

test for carbon dioxide

Bubble the gas through the limewater calcium hydroxide and it will turn milky

test for ammonia

Makes damp red litmus paper turn blue

test for chlorine

When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white

describe how to carry out a flame test

Take a sample of the metal on a wire and put it in a flame , the flame will turn a specific colour , showing what metal it is

Lithium

Red

Sodium

Yellow

Potassium

Lilac

Calcium

Orange - red

Copper

Blue - green

describe tests for Halide ions

First add dilute nitric acid followed by silver nitrate solution

describe tests for these Halide ions

Chloride gives a white precipitate o Bromide gives a cream precipitate o lodide gives a yellow precipitate

Sulfate ions

First add dilute hydrochloric acid followed by barium chloride solution A white precipitate will form when sulfate ions are in this solution

Carbonate ions

Carbonates react with dilute acids to create carbon dioxide This gas can be bubbled through limewater if the limewater goes cloudy the gas is CO₂

describe a test for the presence of water using anhydrous copper ( II ) sulfate

Anhydrous copper II ) sulfate is white When water is present it turns blue

describe a physical test to show whether a sample of water is pure

The purity of water can be tested by evaporating it on an evaporating dish or by measuring its boiling point

know the colours physical states ( at room temperature and trends in physical properties of these elements Chlorine Bromine lodine

Chlorine is a yellow - green gas

• Bromine is a red brown liquid

lodine is a purple solid

use knowledge of trends in Group 7

There is a trend in state from gas to liquid to solid down the group Solid ⚫this is because the melting and boiling points increase as you go down the group , you any halogens above chlorine will be gases and any below iodine will be solids

understand how displacement reactions involving halogens and halides provide evidence for the trend in reactivity in Group 7

A more reactive halogen can displace a less reactive in an aqueous solution of its salt E.g. Chlorine will displace bromine if you bubble the gas through a solution of potassium bromide

Alkanes - ane

C - C

Alkenes - ene

e.g. ethene

Alcohols - ol

ethene ( OH ) e.g. ethanol

Carboxylic acids - anoic

( -COOH ) e.g. ethanoic acid

understand how to classify reactions of organic compounds as substitution , addition and combustion ; knowledge of reaction mechanisms is not required

Addition reactions involve only ONE PRODUCT L.e. 2 reactants 1 product

Substitution reactions

involve TWO PRODUCTS . 2 reactants → 2 products

Combustion involves the reaction of a fuel with OXYGEN

Products are water and carbon dioxide only from hydrocarbons ( if combustion is COMPLETE

hydrocarbon is a

compound of hydrogen and carbon only

General formulae

a type of empirical formula that represents the composition of any member of an entire class of compounds ( e.g. for ethene = CH2 )

Homologous series

series of compounds with the same general formula and similar properties

Functional group

a group of atoms responsible for the chemical reactions of a compound

Isomerism

compounds with the same molecular formula exist in different forms due to different arrangements of atoms ( different forms of isomerism exist

explain why alkanes are classified as saturated hydrocarbons

each carbon has formed its maximum of 4 single bonds Contain no C double bonds therefore the carbons are saturated ,

describe how bromine water can be used to distinguish between an alkane and an alkene

alkenes react with bromine water, turning it from orange to colourless

- alkanes DO NOT react with bromine water- it remains orange

Phenolphthalein turns what an acid and alkaline?

Alkaline turns pink

Acidic turns colorless

What does metal orange turn in alkaline and acidic conditions?

Alkaline turns yellow

Acidic turns red

Litmus solution turns what in alkaline and acidic conditions

Alkaline turns blue

Acidic turns red

How to carry out a titration

1) rinse the burette with hydrochloric acid and fill it with hydrochloric acid

2) use a puppet to transfer a measured volume of sodium hydroxide into a conical flask

3) add a few drops of indicator

4) add the acid from the burette into the flask while swirling

5) stop when the indicator changes color permanently

6) record the final burette reading

7) repeat until concordant results

How could a student show manganese oxide acts as a catalyst in the decomposition of hydrogen peroxide?

Pour hydrogen peroxide in a conical flask, and connect a gas syringe then add manganese oxide, then measure the volume overtime, respect with out a catalyst and keep it at the same temperature and concentration