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### G5 from fundamentals!

Posted: **Mon Oct 02, 2017 7:49 pm**

by **manasa933**

So I used the formula m(initial) x v(initial) = m(final) x v(final) and substituted the following:

m(initial) = 0.079 M

v(initial) = 250 ml

m(final) = 2.15 x 10 (to the power -3)

But in the solutions manual they didn't have the v(initial) anywhere.

Please help!!

### Re: G5 from fundamentals!

Posted: **Mon Oct 02, 2017 8:08 pm**

by **Alyssa Pelak 1J**

I used a stoichiometric approach because the mmol given are Na+ whereas the g and mL given are sodium carbonate. Therefore, you are supposed to find L of Na+

I notice you already found the molarity of the sodium carbonate (Na2CO3) to be .079M. I then took the 2.15 times 10^-3 mol Na+ and multiplied it by the molar ratio 2 mol of Na+ for every 1 mol Na2CO3. Then I multiplied it by 1L there is .079 mol of Na2CO3 (Molarity) to get an answer in mL.

### Re: G5 from fundamentals!

Posted: **Wed Oct 04, 2017 3:22 pm**

by **venning-1J**

for part b,(b) 4.98 mmol CO3 ; would there be 3 moles of CO3 for every mole of Na2CO3?

### Re: G5 from fundamentals!

Posted: **Wed Oct 04, 2017 3:36 pm**

by **Maria1E**

The ratio of CO3 to Na2CO3 is 1:1. The subscript 3 only applies to the oxygen, so there are 3 moles of oxygen for every 1 mole of NaCO3. However, the subscript does not apply to CO3 as a whole so there is only 1 mole of CO3 for every mole of Na2CO3.