Chemistry Paper 1 mistakes

Why did Mendeleev's periodic table become more widely accepted? 3 marks

- mendeleev had predicted the properties of missing elements

- elements were discovered that fit the gaps

- the properties of these new elements matched Mendeleev's predictions

Describe what you would see when sodium reacts with chlorine. 2 marks

- flame

- white solid forms

Describe what you would see when sodium reacts with oxygen in a gas jar. 2 marks

- yellow/orange flame

- white smoke

Suggets why hydrogen fuel cell trains are referred to as 'steam trains'. 2 marks

hydrogen reacts with oxygen in a hydrogen fuel cell, so water vapour is released as a product

Explain why sodium chloride solution cannot be used as the electrolyte to produce sodium metal. 2 marks

Sodium is more reactive than hydrogen, so hydrogen would be produced.

Explain why metals have high melting points and conduct electricity in terms of their bonding and structure. 4 marks

Strong electrostatic forces of attraction between the lattice of positive metal ions in the sea of delocalised electrons (SEFA BLI SODE)

which requires larger amount of energy to break these bonds

Delocalised electrons are free to move throughout the structure

so can carry charge through the structure

Explain why Buckministerfullerene has a low melting point. 3 marks

Consists of individual discreet molecules

Weak intermolecular forces

do not require much energy to break

Explain the attraction in graphite. 2 marks

Strong covalent bonds within the carbon atoms in each layer

weak intermolecular forces of attraction between the layers

A silver anode is used instead of in inert graphite anode. Over time, the anode loses mass. Suggest why. 2 marks

Silver atoms lose electrons to form Ag+ ions

Which dissolve into the solution

Write the half equation at the anode for the electrolysis.

4OH− → O2 + 2H2O + 4e−

Explain why a volumetric pipette used instead of a burette to measure substance in conical flask. 2 marks

Measure one specific volume

burettes measure variable volumes

Explain how an acid can be strong and dilute. 3 marks

Fully dissociates/ionises

In aqueous solution

Low concentration of H+ ions and small amount of acid per unit volume

Explain the trend in the boiling points as you go down group 7. 3 marks

Increases

Molecules become larger and have stronger intermolecular forces

More energy is needed to break these forces

Suggest two observations that could be made when Barium (Group 2) reacts with hydrochloric acid. 2 marks

Bubbles

Get smaller

Explain why the electrical conductivity of the mixture was zero when it has just been neutralised.

Use the equation for the reaction in your answer. 3 marks

there are no ions that are free to move

Barium sulphate is solid and insoluble

Hydrogen ions have reacted with hydroxide ions to form water a covalent substance

Explain why alloys are harder than pure metals. 3 marks

Atoms of different size

Layers become distorted

Cannot easily slide over each other

Describe chemical cell setup. 4 marks

Measure temperature change

When each metal is added to solution

Same mass of metal or concentration of solution

The greater the temperature change the more reactive the metal

Suggest two reasons why nano particles of titanium dioxide are used instead of fine particles for coating self cleaning windows. 2 marks

Greater surface area to volume ratio

Less material needed for same effect

Evidence from the alpha particle sketching experiment led to a change in the model of the atom from the plant pudding model explain how. 4 marks

Most of particles passed straight through the foil

so the mass of the atom is concentrated in the centre

Some particles were deflected

So atom has a positively charged centre

Explain how Chadwick’s work on the atom led to a battery understanding of isotopes. 3 marks

Chadwick discovered neutrons

Isotopes have the same number of protons

But with different numbers of neutrons