The table below shows the substances chosen for a laboratory display about elements and compounds. Small sealed samples of carbon, chlorine, sodium chloride...
Question 1 Report
The table below shows the substances chosen for a laboratory display about elements and compounds. Small sealed samples of carbon, chlorine, sodium chloride and ethene are kept in a box. The teacher uses the melting temperatures to decide which substances need special storage at room temperature. Formulae are included so that students can identify the elements present in each substance.
| substance | formula | melting temperature / °C | classification |
|---|---|---|---|
| carbon | C | 3550 | ................. |
| chlorine | Cl2 | -101 | ................. |
| sodium chloride | NaCl | 801 | ................. |
| ethene | C2H4 | -169 | ................. |
(a) Complete the classification column using element or compound. [4]
(b) Which two substances are gases at a laboratory temperature of 20 °C? [2]
(c) State what the formula NaCl shows about the types of element in sodium chloride. [2]
(d) Use Table 1 to give the substance with the highest melting temperature and the substance with the lowest melting temperature. [2]
(e) Write the balanced chemical equation for the complete combustion of ethene in oxygen. [3]
Answer Details
(a) Carbon is an element because its formula contains one type of atom. Chlorine is an element because \(\mathrm{Cl_2}\) contains only chlorine atoms. Sodium chloride and ethene are compounds because each contains more than one element. [4]
| substance | classification |
|---|---|
| carbon | element |
| chlorine | element |
| sodium chloride | compound |
| ethene | compound |
(b) Chlorine and ethene are gases at \(20\ ^\circ\mathrm{C}\), because their melting temperatures are below this laboratory temperature. [2]
(c) \(\mathrm{NaCl}\) shows that sodium chloride contains two different elements: sodium and chlorine. [2]
(d) Carbon has the highest melting temperature, and ethene has the lowest melting temperature. [2]
(e)
\[\mathrm{C_2H_4+3O_2\rightarrow2CO_2+2H_2O}\]
This is complete combustion, so the products are carbon dioxide and water. [3]
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