Properties and uses of different kinds of steel

3 marks · Normal

A factory has a block of pure iron with a mass of 2000 kg. The factory wants to make mild steel by adding carbon to the iron so that the final carbon content is exactly 0.20% by mass.

Calculate:

(a)

The mass of carbon, in kg, that must be added to the iron to make 2000 kg of mild steel containing 0.20% carbon by mass.

[3 marks]

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4.0 kg (±0.1)

Also accept: 3.99 kg; 4.00 kg

Common mistakes: Calculating 0.2% of 2000 kg as 40 kg (wrong decimal place)

Show mark scheme and worked solution

Marking points

M1 (a) · 1 mark · Chooses correct method: calculates 0.2% (or 0.002) of 2000 kg.

M2 (a) · 1 mark · Correctly sets up and evaluates calculation: 2000 kg × 0.002 or equivalent.

A1 (a) · 1 mark · Final answer correct to suitable precision (4.0 kg, 4 kg, or 4.00 kg, tolerance ±0.1 kg).

Worked solution

The carbon content required = 0.20% of the final mass.

Rearrange to find the mass of carbon:

So, 4.0 kg of carbon must be added.