A solution contains 2.65g of anhydrous Na2O3 in 200cm³ of the solution. Calculate the concentration of the solution in g/dm³ given that (Na2CO3 = 106)

I think you must have meant to calculate the molarity; however, you said g/dm^3 so

2.65 g x (1 dm^3/0.2 cm^3) = ?

Calculate the conc of the solution in g/dm^3

That's what I gave you but I made a typo. That .2 cm^3 should have been 0.2 dm^3.

2.65 g x (1 dm^3/0.2 cm^3) = ?
In any event, the answer is the same.

To calculate the concentration of the solution in g/dm³, we need to find the number of grams of Na2O3 per dm³ of the solution.

First, let's convert the volume of the solution from cm³ to dm³.

Since 1 dm³ is equal to 1000 cm³, we can divide the volume of the solution by 1000:
200 cm³ ÷ 1000 = 0.2 dm³

Now, we need to find the number of grams of Na2O3 in 0.2 dm³ of the solution.

The given mass of Na2O3 is 2.65 g.

Therefore, the concentration of the solution in g/dm³ can be calculated by dividing the mass of Na2O3 by the volume of the solution in dm³:

Concentration (g/dm³) = 2.65 g ÷ 0.2 dm³

Concentration (g/dm³) = 13.25 g/dm³

So, the concentration of the solution is 13.25 g/dm³.