Calculations
What is the relative formula mass of lead bromide (PbBr)?
287
a) what is the name of the positive electrode?
b) what is the name of the negative electrode?
positive - anode
negative - cathode
Name a metal found uncombined in the Earths crust
Gold, Silver, Platinum
What does this symbol mean: ⇌
reversible
What property of metals allows them to be bent / hammered into shape?
They are malleable
If 5.4g of sodium chloride was dissolved in 250cm3 of water, what would be the concentration of the sodium chloride solution? (including the correct units)
5.4 ÷ 0.250 = 21.6 g/dm3
During the electrolysis of molten lead bromide, what would be produced at the cathode?
lead
Describe the process of phytoextraction
Growing plants that absorb metal compounds from the soil.
The plants are then burnt to form ash, from which the metal is extracted.
Ammonia
When a metal corrodes, is it being oxidised, reduced or neither?
oxidised
How many atoms would be in 2 moles of oxygen (O2)
1 mole = 6.02 x 1023 molecules
2 moles = x2
but 2 atoms per molecule, so x2 again:
2.4 x 1024
During the electrolysis of sodium chloride solution, what would be produced at the cathode?
Hydrogen
Give a disadvantage of extracting metals that is common to both phytoextraction and bioleaching
Both very slow
In the Haber process, what are the sources of the hydrogen and nitrogen?
hydrogen: natural gas
nitrogen: the air
What metal is used to galvanise steel to prevent it from rusting?
Zinc
A sample of butane contains 1.44g carbon and 0.3g hydrogen.
Calculate the empirical formula of butane
C2H5
When using graphite electrodes, what is formed at the anode during electrolysis of copper sulfate solution?
oxygen
Why can carbon be used to extract iron from iron ore, but cannot be used to extract aluminium from aluminium ore?
Carbon is more reactive than iron, so will displace it, but carbon is less reactive than aluminium, so cannot displace it.
In an exothermic reaction, what will happen to the yield of the products if the temperature is increased?
It will decrease - the position of equilibrium will move in the endothermic direction
Explain why blocks of magnesium are attached to the hulls of steel ships?
Magnesium is more reactive than iron, so will reactive with the oxygen first. It acts as sacrificial protection
N2 + 3H2 → 2NH3
Calculate the maximum mass of ammonia that could be produced from 2 tonnes of nitrogen. Give the answer to 2 significant figures
2.4 tonnes
In the electrolysis of copper sulfate solution, write a half equation to show the reaction that takes place at the cathode.
Cu2+ + 2e- → Cu
Why do we not use electrolysis to extract iron from iron ore?
Electrolysis requires lots of energy (melting the ore, and the electricity), which is expensive. Displacement by carbon is much cheaper.
2NO2 (g) ⇌ N2O2 (g)
If this reaction is exothermic in the forwards direction, give three factors that could move the position of equilibrium to the left.
Increase temperature
Reduce pressure
Increase concentration of N2O2 / reduce concentration of NO2
Why are alloys stronger than the metals that they are made from?
Different sized atoms disrupt the organisation of the layers, preventing them from sliding over each other as easily