How many moles are contained in the following:

Question

a. 5.89 g KBr
b. 5.3 kg NaCl
c. 7.9 mg KNO3

Answer 1

moles = grams/molar mass

Answer 2

Can you check my answers?
a. 0.0494948 moles
b. 90.686651 moles
c. 0.0000781 moles

Answer 3

Except for small differences, probably due to our not using the exact same molar mass, these are ok. I would make one point. If your prof watches the significant digits, then you have far too many in the first two. Since there are 3 s.f. in 5.89, you may have 3 places in the answer so it should be 0.04949 which rounds to 0.0495 moles KBr. For the second one, it is 90.687 which rounds to 91 moles to two s.f. (there are 2 s.f. in 5.3). Finally, there are 2 s.f. in 7.9 mg and the answer is 0.0000781 which rounds to 0.000078 moles KNO3.