Year 12s: what will be the first way you research your future options? >>

AS chem. Moles calculations. Am I doing this right?

Q:
What mass of Na2O is produced when 2.5g of sodium is burned in oxygen

My A:
Moles of Na = 2.5/23=0.0109
So 0.027 moles of O2
Moles in total = 0.136
Mass of Na=0.136*(23*2)+16=0.843g

Is this right?
Do I need to multiply my answer by 2?
I'm very lost right now

Posted from TSR Mobile

Reply 1

mattcandy3

4Na + O2 -> 2Na2O

is the balanced equation, so no of moles = mass/Mr = 2.5/22.99 = 0.109 moles

ratio is 4:2 so have to divide 0.109 by 2 to get = 0.0545 x Mr mass of Na2O which is 22.99x2 + 16 = 61.98

so answer is 61.98 x 0.0545 = 3.38 grams