Chemistry Past Questions and Answers

(a) State the phenomenon illustrated by the:
(i) spreading of the smell of hydrogen sulphide gas in the laboratory;
(ii) existence of atoms of the same element having different mass numbers
(b) The atomic number of an element is 17. It has different atoms containing 18 neutrons and 20 neutrons, with a relative abundance of 75% and 25% respectively. Calculate the relative atomic mass of the element.

Question 287:

(a) Name the residue obtained on strongly heating the following:
(i) ZnCO\(_3\) in an open crucible;
(ii) CuSO\(_4\), 5H\(_2\)O and then allowing it to cool in a desiccator.
(b) State the colour changes observed on heating and cooling in each case in(a) above.

Question 288:

Mention the respective properties of the following allotropes of carbon that account for their uses as indicated:
(a) diamond used for drilling rocks;
(b) diamond used as jewels;
(c) graphite used as electrodes;
(d) graphite used for slowing down neutrons in nuclear reactors;
(e) wood charcoal used in gas masks.

Question 289:

State which of the following can exhibit geometric isomerism:

Give reason for your answer

Question 290:

(a) X and Y belong to the same period in the Periodic Table is a group I element while Y belongs to group VII. State which of the elements would
(i) be a good oxidizing agent
(ii) have the smaller atomic volume
(iii) have the higher ionization potential
(b) Explain your answer in (a)(i) above.