The student calculated the concentration of sodium chloride in the salt solution. Table 1 shows the results.
The percentage by mass of sodium ions in sodium chloride is 39.3%.
Calculate the mean concentration of sodium ions in the salt solution.

This calculation requires careful data handling and percentage calculation. 1. **Identify Anomalies:** The results are 35.2, 34.6, 36.4, 33.8. To identify an anomaly, we look for the value that is furthest from the others. The range of the three lowest values is 35.2 - 33.8 = 1.4. The value 36.4 is 1.2 away from the next closest value (35.2). It is considered anomalous and should be excluded from the mean calculation to improve accuracy. 2. **Calculate Mean:** The mean of the concordant results is calculated: (35.2 + 34.6 + 33.8) / 3 = 103.6 / 3 = 34.533... g/dm³. This is the mean concentration of the entire sodium chloride compound. 3. **Calculate Percentage:** The question asks for the concentration of sodium ions only. We are told sodium ions make up 39.3% of the mass of sodium chloride. We need to find 39.3% of our calculated mean concentration. 39.3% of 34.533... = (39.3 / 100) * 34.533... = 0.393 * 34.533... = 13.571... g/dm³. 4. **Significant Figures:** The input data is given to 3 significant figures, so the final answer should also be rounded to 3 significant figures: 13.6 g/dm³.