Question

What is the mass of a 2.5-mole sample of magnesium dioxide?

Answer 1

140 g (to 2 sf)

Step-by-step explanation:

The atomic mass of magnesium is 24.305 u.

The atomic mass of oxygen is 15.9994 u.

So, the gram-formula mass of magnesium dioxide, in g/mol, is

`2(15.9994) + 24.305 = 56.3038`

So, the mass of 2.5 moles is (56.3038)(2.5), which is equal to 140 g (to 2 sf)