Chemistry Past Questions And Answers
In the preparation of oxygen by heating KClO3 in the presence of MnO2, only moderate heat is needed because the catalyst acts by
- A) lowering the pressure of the reaction
- B) increasing the surface area of the reactant
- C) increase the rate of the reaction
- D) lowering the energy barrier of the reaction
The oxidation state of calcium is CaCl2 is ___________
- A) +1
- B) +2
- C) +3
- D) +4
(a) State two factors which can affect the rate of a chemical reaction.
(b) 0.72g of magnesium was added to different volumes of 2 mol. per dm\(^3\) hydrochloric acid. The volume of liberated was as measured at room temperature and pressure. The result of the experiment was as tabulated
| vol. of 2 mol. per dm\(^3\) HCl used (cm\(^3\) | Vol. of H\(_2\) evolved in cm\(^3\) (to the nearest 10cm\(^3\)) |
5 15 25 35 45 | 120 360 550 600 600 |
Use the data in the table to plot a graph of the volume of hydrogen liberated against the volume of acid used.
(c) From the graph in (b) above, determine the volume of: (i) hydrogen that would be produced if 50 cm\(^3\) of the acid were added to 0.72g of magnesium.
(ii) the acid which must be added to 0.72 g of magnesium to produce 480 cm\(^3\) of hydrogen;
(iii) the acid needed exactly to dissolve 0.72 g of magnesium completely.
(d) Explain your answer to (c)(iii).
(e) From your answers to (c) above, deduce the: (i) volume of the acid which will dissolve 1 mole of magnesium completely. (Mg = 24)
(ii) volume of hydrogen that would be liberated if 1 mole of magnesium dissolves completely in the acid;
(iii) equation for the reaction between magnesium and hydrochloric acid. Show clearly how you arrived at you answers
View Discussion (0)WAEC 1991 THEORYCauses of hardness of water include the presence of?
- A. calcium tetraoxsulphate (VI).
- B. Magnesium tetraoxosulphate (VI)
- C. Calcium hydrogen trioxocarbonate(IV)
- D. Magnesium hydrogen trioxcocarbonate (IV)
What happens when zinc rod is immersed in copper (II) tetraoxosulphate (VI) solution/
- A. The blue colour of the solution disappears
- B. Electrons flow from copper to zinc
- C. The zinc rod remain undissolved
- D. The copper generate more copper ions
Potassium vapour burns with a
- A. blue flame
- B. brick-red flame
- C. violet flame
- D. golden-yellow flame
The reaction between alkanoic acids and alkanols in the presence of a mineral acid is known as
- A. saponification
- B. hydrolysis
- C. polymerization
- D. esterification
Nitrogen obtained from the liquefaction of air has a higher density than that obtained from nitrogen containing compounds because the former contains
- A. water vapour
- B. oxygen
- C. carbon (IV) oxide
- D. rare gases
Which of the following pieces of deposited if a current of 10A was passed through a solution of copper(ll) salt for 965 seconds? (1F = 96500 C)
- A. 0.005 mole
- B. 0.025 mole
- C. 0.05 mole
- D. 1.00 mole
100cm3 of ethyne was mixed with 240cm3 of oxygen in a combustion chamber. What volume of carbon (iv) oxide is produced?
- A)100 cm3
- B) 24 cm3
- C) 138 cm3
- D) 192 cm3