JAMB Chemistry Past Questions & Answers - Page 258

1,286.

The pH of a solution obtained by mixing 100cm³ of a 0.2M solution of NaOH is?

1.3

7.0

9.7

12.7

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

1,287.

Soap lather is an example of a colloid in which a?

liquid is dispersed in gas

solid is dispersed in liquid

gas is dispersed in liquid

liquid is despersed in liquid

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

1,288.

90.0g of MgCI₂ was placed in 50.0cm³ of water to give a saturated solubility of the salt is 8.0 mol dm³ at the same temperature, what is the mass of the salt left undissolved at the given temperature?

(Mg = 24, Cl = 35.5)

52.0g

58.5g

85.5g

88.5g

View answer & explanation

Correct answer is A

Molar mass of MgCl₂ = 95g
The solubility of MgCl₂ is 8.0/dm³
1 dm³ = 1000cm³
Solubility of g/cm³
8 x 95 → 1000cm³
x → 50
x = (50)/(1000) x (8 x 95) / (1) = 38g
Mass of the salt left undissolved = 90 - 38 = 52.0g

1,289.

If an element X of an atomic number Z and mass number Y is irradiated by an intense concentration of neutrons, the relevant nuclear equation is?

^y_zX + ¹₀n → ^{y - 1}_{z + 1}X

^y_zX + ¹₀n → ^{y + 1}_zX

^y_zX + ¹₀n → ^y_{z + 1}X

^y_zX + ¹₀n → ^{y + 1}_{z - 1}X

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

1,290.

Excess phosphorus was burnt in a gas jar and the residual gas passed successively over concentrated KOH solution and concentration H2SO4 before being collected in a flask. The gases collected are?

carbon (IV) oxide, nitrogen and the rare gases

nitrogen and the rare gases

carbon (IV) oxide, nitrogen (IV) oxide and the rare gases

carbon (IV) oxide

View answer & explanation

Correct answer is B

So phosphorus will remove oxygen by forming P205, KOH will absorb water vapors, and sulfuric acid will react with carbon dioxide thus removing it from the mixture. So nitrogen and rare gases will be left