Correct Answer: B. Wide area network

Explanation

In its simplest form, a wide-area network (WAN) is a collection of local-area networks (LANs) or other networks that communicate with one another. A WAN is essentially a network of networks, with the Internet the world's largest WAN

Correct Answer: A. High density and high growth rate

Correct Answer: A. acceleration is always directed towards a fixed point

Correct Answer: D. -0.6 and 1.6

Correct Answer: C. cowries

Correct Answer: D. national census

Correct Answer: D. change of sharing ratio of vendors

Correct Answer: B. 2.20 V

Explanation

Lost voltage = I x R

= 4 x 0.55

= 2.2V

Correct Answer: C. 40 seconds

Explanation

According to Graham's Law of Diffusion, the rate of diffusion of a gas is inversely proportional to the square root of its molar mass.

Since the rate of diffusion (R) is defined as the volume of gas diffused per unit time (R = \frac{V}{t}), for the same volume of gas, the time taken (t) is directly proportional to the square root of the molar mass (M):

\frac{t_2}{t_1} = \sqrt{\frac{M_2}{M_1}}

Given:

• Time for methane (CH_4), t_1 = 20 seconds

• Molar mass of methane (CH_4), M_1 = 16

• Molar mass of sulphur (IV) oxide (SO_2), M_2 = 64

• Time for sulphur (IV) oxide (SO_2), t_2 = ?

Substitute the values into the formula:

\frac{t_2}{20} = \sqrt{\frac{64}{16}}

\frac{t_2}{20} = \sqrt{4}

\frac{t_2}{20} = 2

t_2 = 20 \times 2 = 40 seconds

Therefore, it will take 40 seconds for the sulphur (IV) oxide to diffuse.

Correct Answer: C. 40 seconds

Explanation

(a)(i) Sketch of Graphical Representation of Charles' Law: Volume (cm\(^3\))

(ii) Volume of O\(_{2(g)}\) required for complete combustion of 2.5 moles of ethanol at s.t.p.

C\(_{2}\)H\(_{5}\)OH\(_{(aq)}\) + 3O2\(_{2}\) -> 3H\(_{2}\)O + 2CO\(_{2(g)}\)

1 mole of ethanol = 3 x 22.4 dm\(^{2}\). of O\(_{2(g)}\)

.-. 2.5 moles of ethanol = 3 x 22.4 dm\(^{3}\) x 2.5

= 168.0 dm\(^{3}\).

(b)(i) Collision theory of reactants rates states that atoms/molecules/ions/particles/reactions involved in a chemical reaction must collide with effective collision before reaction can take place.

(ii) Using collision theory to explain effect of temperature on the rate of a chemical reaction: Increase in temperature makes the reacting molecules to gain kinetic energy and move faster. Where the temperature decreases, the reacting molecules lose kinetice energy and move slower. Frequency of collision and effective collision increase or decrease, therefore rate of reaction increases or decreases.

(c)(i) Esterification is the reaction between an alkanol and alkanoic acid to produce an Alkanoate (ester) and water in the presence of a mineral acid.

(ii) Two uses of alkanoates are: (1) Used in perfumes/cosmetics. (2) Used in artificial flavouring for foods. (3) Used in production of soap. (4) Used as plasticizers. (Any 2)

(iii) Products of the alkaline hydrolysis of ethyl ethanoate are: ethanol (C\(_{2}\)H\(_{5}\)OH) and sodium ethanoate (CH\(_{3}\)COONa) or potassium ethanoate CH\(_{3}\)COOK.

(d)(i) Tin-coated plate corrodes faster.

(ii) Zinc is more reactive than tin, higher in the electrochemical series than tin. When the tin coated plate is exposed, the plate goes into solution and corrodes. In zinc coated (galvanized) plate, it is zinc that dissolves and corrodes hence protecting the plate better and zinc coated plate does not corrode.