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a) Figure 5 shows the structure of a molecule of compound S - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2023 - Paper 1
Question 6
a) Figure 5 shows the structure of a molecule of compound S. (i) Use Figure 5 to deduce the empirical formula of compound S. (ii) The melting points of three sam... show full transcript
Worked Solution & Example Answer:a) Figure 5 shows the structure of a molecule of compound S - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2023 - Paper 1
Step 1
Use Figure 5 to deduce the empirical formula of compound S.
Answer
To deduce the empirical formula, count the number of each type of atom present in compound S. From Figure 5, it is observed that:
- Carbon (C): 6
- Hydrogen (H): 12
- Oxygen (O): 1
The simplest ratio of these atoms is C6H12O. Therefore, the empirical formula is C2H4O.
Step 2
State whether each of these samples, A, B and C, is pure or impure and justify your answers using the information in Figure 6.
Answer
Sample A (160-164 °C), Sample B (166 °C), and Sample C (163-165 °C).
- Sample A: Impure, as the melting point range indicates that it is not a single pure substance but a mixture.
- Sample B: Pure, as it has a sharp melting point at 166 °C, indicating it is likely a single pure substance.
- Sample C: Impure, due to the indicated melting point range, suggesting it is a mixture.
Step 3
Step 4
Explain this difference in boiling points in terms of the structure and bonding of sodium chloride and water and how this difference is used to choose a method to separate sodium chloride solution into pure, dry sodium chloride and pure water.
Answer
Sodium chloride has a high boiling point of 1465 °C because it consists of strong ionic bonds between sodium and chloride ions, requiring a significant amount of energy to break these bonds.
Water, having a boiling point of 100 °C, is held together by weaker hydrogen bonds between water molecules.
The difference in boiling points allows for a separation technique, such as evaporation. When saltwater is heated, water will evaporate at 100 °C, leaving the solid sodium chloride behind, effectively separating the two substances.