You are Here: Home

# (OCR Salters) AS basic Gas Volumes/Entropy question (confused) watch

1. here is a question and the solution to it. i dont however, understand the solution, so some clarification would be awesome

What volume of gas is produced when 15g of sodium is reacted with excess water at r.t.p.?
equation: 2Na + 2H2O -> 2NaOH + H2
Moles of Na = 0.65mol.
From the equation, 2 moles of Na produces 1 mole of H2
(I understand up to here)
So you know 0.65 moles Na produces 0.65/2 = 0.325 moles H2 ok now why did we divide 0.65 by 2? this really has me confused haha.

any help would be much appreciated

thanks <3
2. (Original post by dumb maths student)
here is a question and the solution to it. i dont however, understand the solution, so some clarification would be awesome

What volume of gas is produced when 15g of sodium is reacted with excess water at r.t.p.?
equation: 2Na + 2H2O -> 2NaOH + H2
Moles of Na = 0.65mol.
From the equation, 2 moles of Na produces 1 mole of H2
(I understand up to here)
So you know 0.65 moles Na produces 0.65/2 = 0.325 moles H2 ok now why did we divide 0.65 by 2? this really has me confused haha.

any help would be much appreciated

thanks <3
From your eqn, the only gas produced is hydrogen. and mol ratio shows that mol of H2 = 1/2 x mol of Na reacted.

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 8, 2010
The home of Results and Clearing

### 1,039

people online now

### 1,567,000

students helped last year
Today on TSR

### University open days

1. Keele University
Sun, 19 Aug '18
2. University of Melbourne
Sun, 19 Aug '18
3. Sheffield Hallam University