The table below shows the atomic numbers and boiling points of elements U, V, W, X and Y. (not their actual symbols). Study it and answer the questions that follow.
| Element | Atomic number | Boiling point (0c) |
| U | 3 | 1330 |
| V | 13 | 2470 |
| W | 16 | 445 |
| X | 18 | -186 |
| Y | 19 | 774 |
(a)Select the elements which belong to the same;
(i) Group (1mk)
…………………………………………………………………………………………………………
(ii) Period (1mk)
…………………………………………………………………………………………………………
(b) Which element;
(i) Is gaseous at room temperature? Explain (room temperature = 298K) (2mks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(ii) Does not form an oxide (1mk)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(c) Write the
(i) Formula of the sulphate of element V (1mk)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(ii) Equation for the reaction between Y and W (1mk)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(d) What type of bond exists in the compound formed between U and W? Give a reason for your answer.
(2mks)
………………………………………………………………………………………………………………………………………………………………………………………………………………………………
(e) An aqeous sulphate of element V was electrolysed using carbon electrodes.
Name the products at the;
- Cathode (1mk)
………………………………………………………………………………………………………
- Anode (1mk)
………………………………………………………………………………………………………
answer
1a) i) Same group
U and Y
ii) Same period
V, W and X
b) i) X, B.p = (-186 + 273)
= 87k below room temperature
ii) X
c) i) V3(SO4)2
= V2 (SO4)3
ii) Y(s) + W2 2Y2W(s)
d) Ionic bond
U loses electrons, the electrons gained by W.
e) i) Cathode
Hydrogen gas
ii) Anode
Oxygen gas
