Question 1
- (a) (i)Define the term fermentation.
(ii)Name the catalyst that can be used for this process. [3 marks]
(b)Name two factors which determines the choice of an indicator for an acid-base-titration. [2 marks]
(c)Consider the following reaction equation:
Fe + H2SO4 --> FeSO4 + H2
Calculate the mass of unreacted iron when 5.0 g of iron reacts with 10 cm3 of 1.0 moldm-3 H2SO4.
[Fe – 56.0] [4 marks]
(d)Name one:
(i)heavy chemical used in electrolytic cells;
(ii) fine chemical used in textile industries. [2 marks]
(e)Explain briefly how a catalyst increases the rate of a chemical reaction. [2 marks]
(f) (i) Write the chemical formula for the product formed when ethanoic acid with ammonia.
(ii) Give the name of the product formed in 1 (f)(i). [3 marks]
(gList three properties of aluminium that makes it suitable for the manufacture of drink cans. [3 marks]
(h) State two industrial uses of alkylalkanoates. [2 marks]
(i) Name two steps involved in the crystallization of a salt from its solution. [ 2 marks]
(j) List two effect of global warming. [2 marks]
Observation
In part (a), majority of the candidates defined fermentation as the breakdown of starch to ethanol but did not include CO2 as a product.
In part (b), majority of the candidates could only identify strength of acid and alkali / base as the factors which determine the choice of an indicator for an acid-base titration. Also, majority of them did not know that the strength of an acid or base was not the same as the concentration of acid and base as far as titration is concerned.
In part (c), a good number of the candidates responded to this question but few of them showed all the steps involved in the calculation.
In part (d), majority of the candidates responded to this question. However, many of them wrote formulae when the question required IUPAC names.
In part (e), majority of the candidates could not satisfactorily explain how a catalyst increases the rate of a chemical reaction.
In part (f), majority of the candidates could not write the chemical formula for the product formed when ethanoic acid reacts with ammonia.
In part (g), the attempt on the question was fair. Majority of the candidates listed three properties of aluminium that makes it suitable for the manufacture of drink cans.
In part (h), majority of the candidates stated two industrial uses of alkyalkanoates.
In part (i), majority of the candidates could name two steps involved in the crystallization of a salt from its solution.
In part (j), majority of the candidates listed two effects of global warming.
The expected answers include:
(a)(i) Conversion of (aqueous) glucose/sugar to ethanol / alcohol and release of carbon(IV)oxide (as a by product) OR
Decomposition / breakdown of glucose / starch / carbohydrate to ethanol / alcohol and release of carbon (IV)
(b)- the colour change of the indicator must be sharp - strength of the acid and the base involved in the titration
= 0.56 g
Mass of unreacted Fe = 5.0 – 0.56
= 4.44 g
OR
1 mole of H2SO4 = 1 mole Fe
1,000 cm3 --> 56 g
(d) (i) tetraoxosulphate (VI) acid (Accept conc or dil)
(ii) dyes
(e) Provides an alternative pathway for the reaction to occur by lowering the activation energy.
(f) (i) CH3COONH4
(ii) Ammonium ethanoate
(g) - malleable
- does not corrode
- low density / lightness
- does not react with the (acid in) drinks
(h - production of soap
- flavouring agent
- plasticizers
- solvents / (for e.g. paints, nail varnishes, lacquer, adhesives and cellulose nitrate)
- making of perfumes / cosmetics
(i) - concentration / heating of the solution
- cooling of the solution
- filtration
(j) - sea-level rising
- flooding
- polar ice melting
- glaciers melting
- (severe) climate changes
- (severe) droughts