CIE Chemistry (US-0439): Specimen Questions with Answers 186 - 188 of 240

Question number: 186

Short Answer Question▾

Write in Short

The oxides of carbon and sulfur are gases. The oxides of silicon and phosphorus are not. Explain how these impurities are removed from the impure iron when it is converted into mild steel.

[5 Marks]

Explanation

If want to remove the silicon and phosphorus then we should melt the mild steel because melting point of phosphorus is 44.1°C and silicon is 1,414 °C and iron is 1,538 °C so we should melt till 1,414 °C then both will be removed.

Question number: 187

Short Answer Question▾

Write in Short

  1. Alkenes such as butene and ethene are more reactive than alkanes. Alkenes are used in the petrochemical industry to make a range of products, which includes polymers and alcohols.

(iv) Cracking changes alkanes into alkenes. How could an alkene be converted into an alkane?

[2 Marks]

Explanation

Cracking is the breakdown of a large alkane into smaller, more useful alkanes and alkenes. Simply put, hydrocarbon cracking is the process of breaking a long-chain of hydrocarbons into short ones. This process might require high temperatures and high pressure.

Type of this reaction is exothermic because when this reaction happens then 57.2 J

Question number: 188

MCQ▾

Question

In the history of man, the copper age was followed by the ________ age.

Choices

Choice (4) Response

a.

Copper

b.

Iron

c.

Silver

d.

Golden

Answer

b.

Explanation

In the history of man, the copper age was followed by the iron age.