Chemistry Past Questions and Answers

Calcium hydroxide and ammonium chloride when heated together will give an important product. This compound may be obtained dry by

A Dissolving it in water, recrystallizing it and then drying in the oven
B Passing it through a concentrated aqueous solution of sodium hydroxide
C Passing it through calcium oxide
D Passing it through concentrated sulphuric acid
E Passing it through anhydrous calcium choride

Question 137:

Starch can be converted to ethyl alcohol by

A Distillation
B Fermentation
C Isomerization
D Cracking
E Cooking

Question 138:

The reaction between hydrogen and iodine may be represented by the equation H2(g)+ I2(g) â†’ 2HI(g), and is exothermic. Therefore

A An increase in temperature favours the forword reaction
B An increase in pressure favours the backward reaction
C Both pressure and temperature muct be increased to favour the forward reaction
D A decrease in temperature will favour the forward reaction
E A decrease in pressure and an increase in temperature will favour the forward reaction

Question 139:

Weighed salts Y and Z were left exposed in the laboratory overnight. In the morning Y had gained weight, and Z had become liquid. What conclusion could be drawn about the nature of the two salts?

A Z is efflorescent
B Y and Z are efflorescent
C Y and Z are deliquescent
D Y and Z are hygroscopic
E Y is deliquescent

Question 140:

In the manufacture of iron in the blast furnace, iron (lll) oxide is mixed with coke and limestone, and different reactions occur in the process. Which of the following statements is true with respect to these reactions?

A The coke is a powerful reducing agent and easily converts the iron oxide to iron
B The calcuim carbonate reacts with SiO2 an earthly impurity in the ore, to from calcuim silicate
C The coke will react with the iron produced to form steel
D All the carbondioxide required in the process comes from the decomposition of the calcium carbonate
E The calcium carbonate decomposes to give calcium oxide, which then forms calcium silicate with the earthly impurity