Question

The mass of a quantity of NiCl2 is 24.6 g. How many formula units are in the sample?
A. 3.2 3 10^23 NiCl2 formula units
B. 1.1 3 10^23 NiCl2 formula units
C. 1.9 3 10^27 NiCl2 formula units
D. 5.3 3 10^-21 NiCl2 formula units

Answer 1

@JFraser Can you help?

Answer 2

can you find the molar mass of \(NiCl_2\)?

Answer 3

129.5994 g/mol correct?

Answer 4

good. i'm going to round up to 130, just to make it faster

Answer 5

ONE mole of \(NiCl_2\) will weigh 130g, that's what the molar mass tells us

Answer 6

but you don't have 130g, you've only got 24.6g

Answer 7

Okay.. So, what do I do next to get this? My mind has gone blank..

Answer 8

one mole of anything is always the same \(number\) of things, right?

Answer 9

Yeah?

Answer 10

so \[1 mole \space NiCl_2 \space = \space 6.02*10^{23} \space units \space NiCl_2 = 130g\]

Answer 11

So, would it be D?

Answer 12

it's not D. you need to set up an equality of fractions

Answer 13

\[\frac{6.02*10^{23} units}{130g} = \frac{?? units}{24.6g}\]

Answer 14

Oh!! Okay, so set up that using the numbers in each option to see which one works best?

Answer 15

no, solve the equality for the missing piece and compare it to the options

Answer 16

So, would it be B?

Answer 17

it is