IGCSE Chemistry: Specimen Questions with Answers 77 - 80 of 240

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Question 77

Question

MCQ▾

Calculate the amount of potassium nitrite formed by thermal decomposition of of potassium nitrate.

The chemical reaction taking place is:

[Relative atomic masses: ]

[Give your answer correct to two decimal places]

Choices

Choice (4)

a.

13.75

b.

12.75

c.

11.75

d.

14.75

Answer

b.

Explanation

The chemical reaction taking place is:

RMM of each species in this reaction:

Question 78

Question

MCQ▾

The table shows the boiling points of four members of the homologous series of alcohols.

Boiling for Homologous Series of Alcohols

What is the value of X?

Choices

Choice (4)

a.

b.

c.

d.

Answer

a.

Explanation

Correct answer is C i.e.. 98C because IUPAC name of C3H7OH is 1 – propanol and boiling point of this is 98C.

Question 79

Question

MCQ▾

________ ionise partially and produce less concentration of ions.

Choices

Choice (4)

a.

Strong acids

b.

Strong bases

c.

Weak bases

d.

Weak acids

Answer

c.

Explanation

Weak bases ionise partially and produce less concentration of ions. E. g. , etc.

Question 80

Write in Short

Short Answer▾

The table shows some physical properties of the Group VII elements.

Some Physical Properties of the Group VII Elements

Describe the trend in atomic radius going down the group from chlorine to iodine.

Explanation

Atomic radii tend to get smaller as you move from left to right along the periodic table and larger as you move down the periodic table. Halogens are all part of the same group. However, as you move down the periodic table, the halogens with larger atomic numbers are heavier, have larger atomic radii, and have more protons, neutrons and electrons.

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