Question

how many gram of Na2CO3 should be dissolved to make 100cc of 0.15M Na2CO3

Answer 1

Molarity = given mass / molar mass
     0.15  = x / 106g * 100/1000
         x   =  10.6 * 0.15
        x   =   1.59 g
Therefore, amount of Na2CO3 needed = 1.59 g

Answer 2

Explanation:

Molarity is defined as the number of moles present in a liter of solution.

Mathematically,         Molarity = $\frac{no. of moles}{Volume}$

It is given that molarity is 0.15 M and volume is 100 cc which is also equal to 0.1 liter.

Molar mass of $Na_{2}CO_{3}$ is 106 g/mol.

Therefore, calculate number of moles as follows.

             Molarity = $\frac{no. of moles}{Volume}$

        No. of moles = $Molarity \times volume$

                              = $0.15 M \times 0.1 L$

                              = 0.015 mol

Now, calculate the mass in grams as follows.

          No. of moles = $\frac{mass}{Molar mass}$  

                       Mass = $no. of moles \times molar mass of Na_{2}CO_{3}$

                                 = $0.015 mol \times 106 g/mol$

                                 = 1.59 g

Thus, we can conclude that there will be 1.59 grams of $Na_{2}CO_{3}$ should be dissolved to make 100 cc of 0.15 M $Na_{2}CO_{3}$.