A maintenance report from a ceramics workshop describes a gas-fired kiln that is heating slowly. Table 1 records observations made through the inspection wi...
Question 1 Report
A maintenance report from a ceramics workshop describes a gas-fired kiln that is heating slowly. Table 1 records observations made through the inspection window before the kiln is switched off. The fuel supply is natural gas, which is mainly methane. A black solid has formed on the pale ceramic tiles near the burner.
| observation | result |
|---|---|
| flame colour | yellow with orange tips |
| air inlet | partly blocked by dust |
| ceramic tile near flame | black coating |
| carbon dioxide test on exhaust gas | limewater turns cloudy |
(a) State the name of the black solid on the ceramic tile. [1]
(b) Give the two products of complete combustion of methane. [2]
(c) Write a balanced symbol equation for complete combustion of methane. [2]
(d) Write a balanced symbol equation for incomplete combustion of methane that produces carbon monoxide and water. [2]
(e) Explain why carbon monoxide in the workshop is dangerous. [2]
(f) Give two actions the engineer should take to make the gas reaction more complete. [2]
Answer Details
(a) The black coating is carbon/soot. [1]
(b) Complete combustion of methane produces carbon dioxide [1] and water. [1]
(c) \[\mathrm{CH_4+2O_2\rightarrow CO_2+2H_2O}\]This is balanced: there is one carbon, four hydrogens, and four oxygens on each side. [2]
(d) \[\mathrm{2CH_4+3O_2\rightarrow2CO+4H_2O}\]This balanced equation represents incomplete combustion forming carbon monoxide. [2]
(e) Carbon monoxide is poisonous because it prevents blood carrying enough oxygen, by binding to haemoglobin. [2]
(f) Any two suitable actions are: clear the air inlet, increase the air/oxygen supply, service or unblock the burner, or ensure gas and air mix properly. These provide enough oxygen for complete combustion. [2]
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