NECO Past Questions and Answers - Page 99

491.

Why does the treatment of cotton fabrics with dilute acids weaken the materials?

A.

Cotton is hydrolysed completely to glucose

B.

The fabrics are soluble in dilute acids

C.

The molecular chains are partially broken

D.

The molecular chain length f the fabric increases

E.

The thread holding the fabric together Is completely destroyed.

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

492.

An organic compound gave the following results on analysis: C = 29.3% ; H = 5.7%; Br = 65%.
What is the empirical formula of the compound? [C = 12, H = 1, Br=80]

A.

CH₃Br

B.

C₂H₅Br

C.

C₃H₅Br

D.

C₃H₇Br

E.

C₄H₉Br

View answer & explanation

Correct answer is D

No explanation has been provided for this answer.

493.

What mass of copper is deposited when 6.5g of granulated zinc reacts with excess copper(II) tetraoxosulphate(VI) solution?

The equation for the reaction is: Zn(s) + \( CuSO_4(aq)→ ZnSO_4(aq)+ Cu(s)\)[CU= 64; Zn=65]

A.

3.2 g

B.

3.25 g

C.

6.4 g

D.

6.5 g

E.

64.0 g

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

494.

Which element is the most electronegative?

A.

calcium

B.

fluorine

C.

iodine

D.

oxygen

E.

sodium

View answer & explanation

Correct answer is B

No explanation has been provided for this answer.

495.

What change will occur to the equilibrium mixture
\( 2CrO^{2-}_4(aq) + 2H^+(aq) ⇔ Cr_2O^{2-}_7(aq) + H_2O(l) \) when excess sodium hydrogen solution is added?

A.

A yellow precipitate of Cr(OH)3 is formed

B.

An orange precipitate of Cr(OH)3 is formed

C.

The colour changes from orange to yellow

D.

The colour changes from yellow to orange

E.

There is no visible reaction.

View answer & explanation

Correct answer is C

No explanation has been provided for this answer.

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