WAEC Chemistry Past Questions & Answers - Page 118

586.

The formula of mercury (l) dioxonitrate (III) is

A.

HgNO3

B.

Hg2NO2

C.

Hg2(NO2)2

D.

Hg(NO3)2

Correct answer is C

No explanation has been provided for this answer.

587.

Consider the reaction represented by the following equation: xCH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + zH\(_2\)O. The values of x,y and z respectively, are

A.

2,3 and 4

B.

2, 4 and 3

C.

1,2 and 3

D.

1, 3 and 5

Correct answer is A

xCH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + zH\(_2\)O

Balancing the equation, we have

C = x (on the left) and 2 (on the right)

⇒ x = 2

2CH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + zH\(_2\)O

On the left, H = 8 and on the right = 2z

⇒ 2z = 8 ; z = 4

2CH\(_3\)OH + yO\(_2\) → 2CO\(_2\) + 4H\(_2\)O

On the right, O = 4 + 4 = 8.

On the left, O = 2 + 2y

⇒ 2 + 2y = 8

2y = 6 ; y = 3

x, y, z = 2, 3, 4.

588.

The number of sulphur atoms in 3.20g of SO\(_{2(g)}\) is [O = 16.0;S = 32.0; Avogadro constant = 6.02 x 10\(^{23}\)]

A.

3.01 x 1022

B.

6.02 x 1022

C.

6.02 x1023

D.

1.20 x 1024

Correct answer is A

32g of sulphur = 64g / 6.02 x 10\(^{23}\) atoms of SO\(_2\)

xg of sulphur = 3.2g of SO\(_2\) 

: 1.6g of sulphur is present in 3.2g / 3.01 x 10\(^{23}\) atoms of SO\(_2\)  

589.

Consider the following reaction equation: CaCO\(_{3(s)}\) + 2HCI\(_{(aq)}\) → CaCl\(_{2(aq)}\) + H\(_2\)O\(_{(l)}\) + CO\(_{2(g)}\). What mass of CaCI\(_2\) would be obtained when 25.0g of CaCO\(_{3(s)}\) is reacted with excess HCI\(_{(aq)}\)? [CaCO\(_3 = 100; CaCI\(_2\) = 111]

A.

4.00g

B.

4.44 g

C.

18.9 g

D.

27.8 g

Correct answer is D

CaCO\(_3\) + 2HCI → CaCI\(_2\) + H\(_2\)O + CO\(_2\)

100g CaCO\(_3\) will produce 111g CaCI\(_2\)

25g CaCO\(_3\) will produce x ,

x = \(\frac{25 x 111}{100}\)

= 27.75 \(\approxeq\) 27.8g

590.

MgO does not readily dissolve in water because

A.

of its high melting point

B.

it is a covalent compound

C.

it forms a hydroxide when dissolved in water

D.

its lattice energy is higher than its hydration energy

Correct answer is D

No explanation has been provided for this answer.