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由于水的导电性很弱，为了增强水的导电性，做电解水实验时常在水中加入少量氢氧化钠固体(在水电解过程中，氢氧化钠质量和性质都不发生变化)。把 180 克氢氧化钠...

Mar 19, 2024

由于水的导电性很弱，为了增强水的导电性，做电解水实验时常在水中加入少量氢氧化钠固体(在水电解过程中，氢氧化钠质量和性质都不发生变化)。把 180 克氢氧化钠的质量分数为1%的溶液进行电解，电解结束后氨氧化钠的质量分数为1.2%. 180 克氢氧化钠溶液中含有溶质氨氧化钠的质量为多少?

Solution

Calculate the mass of solute before electrolysis: Given that the mass percentage of sodium hydroxide (NaOH) in the solution is 1%, we can calculate the mass of NaOH in the 180 g solution. The mass percentage formula is

\text{mass percent} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100\%

Calculate the mass of NaOH: Using the mass percentage formula,

1\% = \frac{\text{mass of NaOH}}{180 \text{ g}} \times 100\%

. Solving for the mass of NaOH gives us

\text{mass of NaOH} = \frac{1}{100} \times 180 \text{ g}

Calculate the mass of the solution after electrolysis: After electrolysis, the mass percentage of NaOH is 1.2%, but the mass of the solution remains the same, 180 g, because the question states that the mass and properties of NaOH do not change during the process

Calculate the mass of water in the solution after electrolysis: Since the mass of NaOH does not change, the increase in mass percentage is due to the loss of water during electrolysis. The mass of water lost can be calculated by the difference in mass percentages before and after electrolysis

Answer

The mass of solute sodium hydroxide (NaOH) in the 180 g solution before electrolysis is 1.8 g.

Key Concept

Mass percentage of a solute

Explanation

The mass percentage of a solute in a solution is calculated by dividing the mass of the solute by the total mass of the solution and multiplying by 100%.