You are Here: Home

# Quick Question watch

1. ...............
2. (Original post by benzenee)
Our experiment was to measure enthalpy changes, I managed to do the first section of it which was solvation -
Q = C M Delta T, which for me was 4.184 * 70g (this is of distilled water)
* 6 (temp change) = 1757.28
then moles = 1.72 grams of NaOH / 40g/mol = 0.043mol
Then determined enthalpy - 1.75728 / 0.043 = 40.867

Now we then placed 70ml of 1.0 HCL acid into calorimeter, measured temp of NaOH from first experiment, when same temp and cool down, then added it to the HCL, so now to determine Q, it is still 4.184 * is it 140g as both liquids are added and m is mass of water in calorimeter, or just the 70g from the first part?

Final Question, how do i figure out the moles, as i did 70g of the solution / 40 = 1.75 mol, but it means it has increased, when no more NaOH has been added, so should i stick with the original amount of 1.72g / 40 = 0.043 or change to 70ml including NaOH and H20?

Thanks
Both liquids are being heated up so it must be 140g

The maximum number of moles is limited by the limiting reagent. As they react together in a 1:1 ratio then this is the component with the fewer moles:

If 0.043 moles of NaOH have been used and 70ml of 1.0 M HCl ( = 0.07 mol) then NaOH is the limiting reagent.

Your energy must be divided by 0.043 ....
4. (Original post by benzenee)
you just did ...

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: April 18, 2013
Today on TSR

### Struggling to get going with your revision?

Get going with the all day revision thread

### Uni strikes! How do they affect you?

Discussions on TSR

• Latest
Poll
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE