Question

Calculate the number of particles in 7.8 mol MgCl2(s). Indicate the correct type of particle (atom, molecule, ion, or formula unit).
a) 4.7 x 10^24 formula units
b) 1.3 x 10^23 formula units
c) 4.7 x 10 ^24 molecules
d) 1.3 x 10^23 molecules

Answer 1

it will be 7.8 * 6.02*10^23 of something

Answer 2

@oobleck I feel like the answer is a) 4.7 x 10^24 formula units, am I correct?

Answer 3

First, I notice that both a and c answers are the same.
The correct answer isn't one of the choices. .MgCl2 in water gives you Mg^2+ + 2Cl^- for every molecule of MgCl2.
So you get 7.8 mols x 6.02E23 particles/mol x 3 ions = ? ions

Answer 4

ionic compounds are generally expressed in formula units

Answer 5

However, the question is about the number of particles and there are 3 ions/formula unit of MgCl2. The way I see it there are zero formula units of MgCl2 because they are not there as MgCl2 but as Mg ions and Cl ions.

Answer 6

How would I go about solving it?

Answer 7

Read the last sentence of my first answer.