NECO Chemistry Past Questions & Answers - Page 4

16.

The Ideal Gas Law is expressed mathematically as

A.

P1 /T1 = P2/T2

B.

P1/V1 = P2V2

C.

PV =nRT

D.

PV =KT

E.

V1/T1 = V2/T2

Correct answer is C

The empirical relationships among the volume, the temperature, the pressure, and the amount of a gas can be combined into the ideal gas law, PV = nRT.

17.

Two elements X and Y with electronic configurations 2,8,2 and 2,8,7 respectively, are likely to combine by _________bonding

A.

covalent

B.

dative

C.

electrovalent

D.

hydrogen

E.

metallic

Correct answer is C

No explanation has been provided for this answer.

18.

The furring of kettles and boilers are caused by

A.

calcium hydroxide

B.

calcium hydrogen trioxocarbonate (IV)

C.

calcium trioxocarbonate (IV)

D.

calcium tetraoxocarbonate

E.

magnesium tetraoxocarbonate (VI)

Correct answer is C

The furring of kettles or boilers - this is as a result of the decomposition of Ca(HCO3)2 into CaCO3, and this coats the inside of a kettle or boiler used in heating water containing dissolved Ca(HCO3)2.

19.

Which of the following metals is NOT extracted by electrolysis?

A.

Aluminium

B.

Calcium

C.

iron

D.

Magnesium

E.

Sodium

Correct answer is C

No explanation has been provided for this answer.

20.

What mass of copper in gram would be deposited by a current of 1.00ampere passing for 965 seconds through copper(II) tertraoxosulphate (VI) solution? [Cu 63.5; If = 96500c]

A.

0.32

B.

0.64

C.

3.18

D.

6.35

E.

9.65

Correct answer is A

Recall that two faradays ( 2 X 96500 ) will be required to discharge 1 mole of a divalent ion like Cu.

2 X 96500 will deposit 63.5g of Cu

And 965C wiil deposit  x-grams

CROSS MULTIPLY

(965 X 63.5) ÷ ( 2 X 96500)

= 0.3175