GCSE Edexcel Chemistry Combined Science Water: 4 (a) Air contains several gaseo

Question

4 (a) Air contains several gaseous elements. 
Which of these shows the three most common gaseous elements in air, listed in order from the most common to the least common?

A  oxygen, chlorine, nitrogen 
B  nitrogen, oxygen, hydrogen 
C  oxygen, nitrogen, helium 
D  nitrogen, oxygen, argon

(b) The density of a gas can be found using the equation

density = \frac{mass}{volume}

A student carried out an experiment to find the density of argon. 
The mass of a stopper and flask, containing no gas, was known. 
The flask was completely filled with argon and its mass measured. 
Figure 2 shows the results the student wrote down.

Mass of stopper and flask in g     78.639 
Mass of stopper and flask full of argon in g  79.120 
Volume of flask in cm³  250.0

Figure 2

(d) Much of the carbon dioxide present in the Earth’s early atmosphere dissolved into the oceans. 
This led to the formation of compounds including calcium carbonate, CaCO₃. 
Some of the calcium carbonate reacted with magnesium ions to form dolomite, CaMg(CO₃)₂. 
Complete the ionic equation for the reaction of calcium carbonate with magnesium ions.

CaCO₃ + _______________ → CaMg(CO₃)₂ + Ca²⁺

(d) P and Q are both mixtures of gases. 
One has the same composition as the early atmosphere and the other has the same composition as the current atmosphere.

Tests are carried out on gas mixtures P and Q.

The test for carbon dioxide is to bubble the gas into limewater; if carbon dioxide is present calcium carbonate is formed.

The results of the tests are shown in Figure 4.

Figure 4

Explain, using the data in Figure 4, which gas mixture represents the early atmosphere.

4 (a) Air contains several gaseous elements - Edexcel - GCSE Chemistry Combined Science - Question 4 - 2020 - Paper 1

Worked Solution & Example Answer:4 (a) Air contains several gaseous elements - Edexcel - GCSE Chemistry Combined Science - Question 4 - 2020 - Paper 1

Which of these shows the three most common gaseous elements in air, listed in order from the most common to the least common?

Use the results to calculate the density of argon in g cm⁻³.

Complete the ionic equation for the reaction of calcium carbonate with magnesium ions.

Explain, using the data in Figure 4, which gas mixture represents the early atmosphere.

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