TeXes Science Practice Test

How many grams of Na2SO4 are required to prepare a 10 dm³ of an 8% solution?

1. 750 g

2. 860 g

3. 1000 g

4. 1200 g

The correct answer is: 860 g

To determine the correct amount of sodium sulfate (Na2SO4) required to prepare a 10 dm³ solution at an 8% concentration, it's essential to understand what an 8% solution means. An 8% solution indicates that there are 8 grams of solute (in this case, Na2SO4) for every 100 mL of solution. First, we need to convert the volume of the solution from dm³ to mL because the percentage is typically referenced per 100 mL of solution. Since 1 dm³ is equivalent to 1000 mL, 10 dm³ is equal to 10,000 mL. Next, we calculate how much Na2SO4 is needed for the entire volume of 10,000 mL. To find the mass of Na2SO4 in an 8% solution: 1. Set up the equation based on the percentage: - For every 100 mL, there are 8 grams of Na2SO4. - Therefore, in 10,000 mL (which is 100 times 100 mL), the amount of Na2SO4 needed would be: \[ 8 \text