The question requires us to calculate the mass of a certain compound in a solution, given its molar mass, the volume and molarity of the solution.
The following data was provided by the question:
molar mass of compound = 67.91 g/mol
volume of solution = 683.2 mL
molarity of solution = 1.2 M = 1.2 mol/L
The molarity of a solution is defined as:
where C is the molarity (in mol/L), n is the number of moles of solute (in mol) and V is the volume of solution (in L).
Also, the number of moles of a compound can be defined as:
where n is the number of moles (in mol), m is the mass of a sample (in g) and M is the molar mass of the compound (in g/mol).
We can use the definition of number of moles and replace it in the first equation, where the molarity of a solution is given. Doing this, we'll have the following equation:
where we can use the mass, molar mass and volume to find the molarity.
Rearranging the equation to calculate the mass, as required by the question, we'll have:
Now, we can use the values provided by the question to calculate the mass of the given compound using the previous equation (note that we must divide the volume as given by 1000 in order to convert the quantity from mL to L):
Therefore, there are 55.68 g of the given compound in the solution provided by the question.