You are Here: Home

# Chemistery watch

1. A student mixes 100 cm3
of 0.200 mol dm–3 NaCl(aq) with 100 cm3
of
0.200 mol dm–3 Na2CO3(aq).
What is the total concentration of Na+
ions in the mixture formed?

I know that the answer is 0.300 mol dm-3 but how do you work it out?
2. Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

You can also find the Exam Thread list for A-levels here and GCSE here.

Just quoting in Puddles the Monkey so she can move the thread if needed
Spoiler:
Show
(Original post by Puddles the Monkey)
x
3. (Original post by 12aryana)
A student mixes 100 cm3
of 0.200 mol dm–3 NaCl(aq) with 100 cm3
of
0.200 mol dm–3 Na2CO3(aq).
What is the total concentration of Na+
ions in the mixture formed?

I know that the answer is 0.300 mol dm-3 but how do you work it out?

NaCl(aq) = Na+(aq) + Cl-(aq)

Na2CO3(aq) = 2Na+(aq) + CO32-(aq)

As you can see one mole of NaCl gives one mol of Na+ ions
Also, one mole of Na2CO3 gives two mol of Na+ ions

So from NaCl, using conc. x volume = moles

0.2 x 0.1 = 0.02 moles

From Na2CO3

0.2 x 0.1 x 2 = 0.04 moles

Therefore, total moles of ions

0.04 + 0.02 = 0.06 moles

This is in a total volume now of 0.2 dm-3 (2 x 100 cm3)

Final concentration = 0.06/0.2 = 0.3 mol dm-3

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: March 31, 2016
Today on TSR

### University open days

1. University of Cambridge
Wed, 26 Sep '18
2. Norwich University of the Arts
Fri, 28 Sep '18
3. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
Poll

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