Question

A student must prepare 7.00 L of 0.100 M Na2CO3 (106 g/mol). Which is the best procedure for preparing this solution

Answer 1

To prepare a 0.100 M Na2CO3 solution, dissolve 74.2 g of Na2CO3 in less than 7.00 L of water, then add water to reach exactly 7.00 L using a volumetric flask for accuracy.

Step-by-step explanation:

Preparing a 0.100 M Na2CO3 Solution

The task is to prepare 7.00 liters of a 0.100 M solution of sodium carbonate (Na2CO3). First, we need to calculate the amount of Na2CO3 needed using the molar mass of Na2CO3 which is 106 g/mol.

To calculate the moles of Na2CO3 required:

1. Use the equation Molarity (M) = moles of solute / volume of solution (L).
2. To find the moles of Na2CO3 needed, multiply the molarity by the volume: 0.100 M × 7.00 L = 0.700 moles Na2CO3.
3. Calculate the mass of Na2CO3 needed by multiplying the number of moles by the molar mass: 0.700 moles × 106 g/mol = 74.2 g of Na2CO3.

To prepare the solution:

1. Add less than 7.00 L of water to a volumetric flask.
2. Dissolve 74.2 g of Na2CO3 into the water in the flask.
3. Once dissolved, add water until the total volume is up to the 7.00 L mark on the flask.
4. Mix the solution thoroughly to ensure homogeneity.

Using a volumetric flask is crucial as it ensures accuracy in the final solution volume.

Answer 2

Measure 74.2 g Na2CO3 and add H20 until the final homogeneous solution has a volume of 7.00 L

Step-by-step explanation:

The best procedure is

Mole of

`Na_2CO_3 = Volume * molarity\\\\= 7.00 L * 0.100 mol\\\\`

= 0.700 mol

The mass of

`Na_2Co_3 = Moles * molar\ mass \\\\= 0.700 mol * 106 g/mol`

= 74.2 g

So as per the above calculation, the option 3 is correct as the solution volume is 7.00 L so the same is to be considered

hence, all other options are wrong