Chemistry Past Questions and Answers

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 142:

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

Question 143:

Which of the following statements is true?

A An increase in the temperature of a given mass of gas increases the number of gas molecules
B An increase in the temperature of the gas does not affect the kinetic energy
C An increase in the pressure of the gas is proportional to the increase in volume
D A increase in the pressure of a gas is proportional to the decrease in volume at constant temperature
E A decrease in the pressure of the gas decreases the number of gas molecules present

Question 144:

the vapour density of a gas may be defined as

A The mass of a unit volume of the gas compared to an equal volume of water vapour
B The mass of a unit volume of the gas compared to an equal volume of hydrogen
C The mass of a unit volume of the gas compared to an equal volume of oxygen
D The mass of a unit volume of the gas minus the vapour pressure of water
E Two times the relative molecular mass of the gas

Question 145:

The reaction 3C(s) + 2Fe2O3(s) = 4Fe(s) + 3CO2(g): \(\Delta\)H =46.0 kJ is

A Isothermic
B Adiabatic
C Isobaric
D Endothermic
E Exothermic