Question

If 6.35 g of cu(no3)2 is dissolved in water to make a 0.750 m solution, what is the volume of the solution (in ml)?

Answer 1

First, we need to find out how many moles we have of $Cu ( NO_{3} )_{2}$ if we are given 6.35g.

We need to calculate the molar mass of the molecule:

Cu: 63.546g
N: 14.01g * 2 = 28.02g
O: 15.999g * 6 = 95.994

Add them together to get: 187.56g

So now we need to find the number of moles we are given. This can be done by setting up a multiplication equation and cancelling the units:

$\frac{1mole}{187.56g}* \frac{6.35g}{1}=0.034 mol _{Cu( NO_{3} )_{2} }$

So now that we know the number of moles that we have, we can use the molarity equation to find the volume of the solution. The molarity equation is:

$Molarity= \frac{moles}{Liters}$

So since we are given the molarity in the equation (0.750 M), we can plug in the molarity and moles to find the volume of the solution:

$0.750= \frac{0.034mol}{volume(L)}$

$volume(L)=0.04533L$

So now we know that the volume is 0.04533 Liters; however the question asks for the answer in milliliters. To do this, we must multiply by 1000:

$\frac{0.045L}{1} * \frac{1000mL}{1L}=45.33mL$

So the volume of the solution (in mL) is 45.33 mL.