## Practice Worksheet Week 1 Question 3 [ENDORSED]

Kristen Laulette 1C
Posts: 10
Joined: Fri Apr 06, 2018 11:03 am

### Practice Worksheet Week 1 Question 3

I am going over week 1 material, and I did the question: What is the mass percent of the elements in Sr(NO2)2?

I found the atomic mass of each, multiplied it by their subscripts, and got the molecular mass to be 147.6322 g/mol.

I then divided the molecular mass by each one of the elements' mass in the compound and multiplied it by 100%. I got Sr as 59.35%, N as 18.98%, and O as 21.67%. The answers are:

Sr: 48.78% N: 15.60% O: 35.63%

Did I do something wrong?

Jaquelinne Rodriguez-Lopez 1L
Posts: 38
Joined: Mon Apr 09, 2018 1:38 pm
Been upvoted: 1 time

### Re: Practice Worksheet Week 1 Question 3  [ENDORSED]

the molar mass of the compound should be 179.62 g.mol^-1:
Sr: 1 * 87.62
N: 2 * 14.00
O: 4 * 16.00
when an equation has a compound multiplied by a subscript outside the parenthesis, make sure you distribute through multiplication the value of the subscript to each element inside the (____). so, in this case, you have 1 Sr, 2 N, and 4 O :)

Chris Fults 1C
Posts: 27
Joined: Wed Nov 15, 2017 3:01 am

### Re: Practice Worksheet Week 1 Question 3

Did you count 2 nitrogens and 4 oxygens because the two at the bottom of the parenthesis means you multiply with whats inside of them? There would be 2 nitrogens and 4 oxygens. The mass of nitrogen would be 28 and the mass of oxygen would be 64. I did this and got Sr= 49%, O= 36%,and N=16%.

Kristen Laulette 1C
Posts: 10
Joined: Fri Apr 06, 2018 11:03 am

### Re: Practice Worksheet Week 1 Question 3

Oh, I did make that mistake, thank you both so much!