We can find molarity using the following equation:
In this problem, our solute is CaCO3, and we have 15.7 g of it. To express this amount in moles, what we do is to divide by the molar weight of CaCO3. (Always that you want to pass from grams to moles you do this, just to divide the amount that you have by the molar weight of the substance).
This is:
Now, we have 275mL of solution and this is 0.275L of solution. (To pass from mL to L we just divide by 1000).
Finally, replacing in the formula to find molarity, we have:
The answer is 0.57M.
