ESAT ESAT Chemistry 3

Question 1

What is the empirical formula of a compound with 40% C, 6.67% H, and 53.33% O by mass?

Accepted Answer

CH₂O

Answer

Dividing by atomic masses: C:H:O = 40/12 : 6.67/1 : 53.33/16 ≈ 3.33 : 6.67 : 3.33 = 1:2:1 → CH₂O.

Question 2

In ESAT Chemistry, what does the rate equation r = k[A]²[B] indicate?

Accepted Answer

Second order in A and first order in B, third order overall

Answer

The rate equation shows the reaction is second order in A, first order in B, and third order overall.

Question 3

What is a buffer solution?

Accepted Answer

A solution that resists pH change on addition of small amounts of acid or base

Answer

A buffer solution contains a weak acid and its conjugate base, resisting pH change when small amounts of acid or alkali are added.

Question 4

Which periodic trend describes the decrease in atomic radius across a period (left to right)?

Accepted Answer

Increasing nuclear charge attracting electrons more strongly

Answer

Across a period, protons increase while electrons are added to the same shell, so greater nuclear charge pulls electrons closer.

Question 5

What is produced when an acid reacts with a base?

Accepted Answer

Salt and water

Answer

An acid-base neutralisation reaction produces a salt and water as products.

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