Calculation of Mass of Sodium Sulphate for 20% Solution:

To calculate the mass of sodium sulphate required to prepare a 20% solution in 100g of water, we need to consider the definition of a 20% solution and use the formula:

Mass percent = (mass of solute / mass of solution) x 100

In this case, the solute is sodium sulphate, and the solution is a mixture of sodium sulphate and water.

Step 1: Determine the Mass of the Solution:

The mass of the solution is given as 100g of water.

Step 2: Determine the Mass of the Solute:

We need to find the mass of sodium sulphate required to prepare the solution. Let's assume it is "x" grams.

Step 3: Calculate the Mass Percent:

The mass percent of the solution is given as 20%.

20% = (mass of sodium sulphate / (mass of sodium sulphate + 100g)) x 100

Simplifying the equation, we get:

20 = (x / (x + 100)) x 100

Step 4: Solve for x:

To find the value of x, we can rearrange the equation as follows:

20(x + 100) = 100x

20x + 2000 = 100x

2000 = 80x

x = 2000 / 80

x = 25 grams

Therefore, the mass of sodium sulphate required to prepare a 20% solution in 100g of water is 25 grams.

Summary:

To summarize the calculation, we followed the steps as mentioned below:

1. Determined the mass of the solution (100g of water).
2. Assumed the mass of sodium sulphate as "x" grams.
3. Calculated the mass percent using the formula (20 = (x / (x + 100)) x 100).
4. Rearranged the equation and solved for x.
5. Found that the mass of sodium sulphate required is 25 grams.

By following these steps, we can accurately determine the mass of sodium sulphate needed to prepare a 20% solution in 100g of water.

20 gm of sodium sulphate put the values in the formula to find mass percentage of solution