This gas is used in welding cylinders and is supplied as a mixture of oxygen and argon. A technician checks a cylinder after delivery. The label states that...
Question 1 Report
This gas is used in welding cylinders and is supplied as a mixture of oxygen and argon. A technician checks a cylinder after delivery. The label states that it contains 98% argon and 2% oxygen by volume. Both gases are colourless, and neither can be separated from the other using filter paper. The technician compares the cylinder with a sample of pure oxygen, which supports combustion much more strongly. The gases are stored under pressure, so the cylinder must not be heated during the test.
(a) State whether the cylinder contents are an element, compound or mixture. [1]
(b) Give one reason for your answer. [1]
(c) Calculate the volume of oxygen in 600 cm3 of the cylinder gas. [2]
(d) Name the method used industrially to separate oxygen and argon from liquid air. [1]
(e) Explain why filtration cannot separate the two gases. [2]
(f) Which gas is present in the larger volume: oxygen or argon? State its volume in 600 cm3. [1]
Answer Details
(a) The cylinder contains a mixture. [1]
(b) It contains two gases, argon and oxygen, which are not chemically combined. [1]
(c)
\[\frac{2}{100}\times600\text{ cm}^3=12\text{ cm}^3\]
The oxygen volume is 12 cm3. [2]
(d) Industrially, oxygen and argon are separated from liquid air by fractional distillation. [1]
(e) Filtration separates an insoluble solid from a liquid. Both oxygen and argon are gases, so neither is a solid that can be trapped by filter paper. [2]
(f) Argon is present in the larger volume:
\[\frac{98}{100}\times600\text{ cm}^3=588\text{ cm}^3\]
[1]
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