During a chemistry lesson, almost all of the students got the answer for a question wrong. When the lesson had ended the teacher hadn't yet told us the problem with our method and most of us are quite passionate to find the correct answer now.

Mass of solute: 12g of MgCl_{2}

The volume of liquid:?

Concentration mol/dm^{3}: 1.5 mol/dm^{3}

Concentration g/dm^{3}: 19.6/dm^{3}

In a previous lesson, we had learnt that:

Concentration mol/dm^{3} = number of moles / volume (dm^{3})

so rearranging this gives:

Volume = number of moles / Concentration

To work out the number of moles I had taken the mass (12g) and divided it by its relative formula mass (95):

Number of moles = 12/95 = 0.12631578947

then I substituted it into the earlier equation: Volume = number of moles / Concentration

Volume = 0.126 / 1.5 = 0.0084dm^{3}

However, the teacher's answer was 8dm^{3}, though I'm pretty sure my answer is wrong I don't know where I went wrong. All help is appreciated

I've attached the worksheet as pdf where the question is from but it has my messy writing over some of it so it may be unclear.