IGCSE Chemistry Paper-1: Specimen Questions with Answers 79 - 82 of 99

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Question 79

Question

MCQ▾

What is a redox reaction?

Choices

Choice (4)

a.

Gain of electrons by a molecule, atom or ion.

b.

Loss of electrons by a molecule , atom or ion.

c.

Both a. and b. are correct

d.

Question does not provide sufficient data or is vague

Answer

c.

Explanation

The reactions in which oxidation and reduction takes place simultaneously are known as redox reactions. Loss of electrons by a molecule, atom or ion is oxidation (whereas Gain of electrons by a molecule, atom or ion is known as reduction) .

Question 80

Question

MCQ▾

What will be the pH of 0.10 M of HCl solution?

Choices

Choice (4)

a.

2

b.

1

c.

4

d.

3

Answer

b.

Explanation

As we know that

Therefore,

So, pH = 1. ‎Hence, pH of 0.10 M HCl solution is 1.

Question 81

Question

MCQ▾

Which of this structure does not represent an allotropic form of carbon?

Which is Not an Allotrope of Carbon

Choices

Choice (4)

a.

A

b.

C

c.

B

d.

D

Answer

d.

Explanation

In the above figures Fig A represents Diamond, fig B represents Graphite, Fig C represents fullerenes. Fig D represents coal which is not an allotropic form of carbon.

Question 82

Question

MCQ▾

What is the chemical formula for plaster of paris?

Choices

Choice (4)

a.

b.

c.

d.

Question does not provide sufficient data or is vague

Answer

a.

Explanation

The chemical name of plaster of paris is Calcium sulphate hemi hydrate.

It is prepared by heating gypsum at 100 degree Celsius in rotary kilns, where it gets partially dehydrated.

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