Help with a chemistry question!

Announcements
#1
Its located on the OCR sample paper for 2015 if anyone is wondering. It states:

A student mixes 100cm3 of 0.200 mol dm-3 NaCl (Aq) with 100cm3 of 0.200 mol dm-3 (Na2)C(O3).

What is the total concentration of Na+ ions in the mixture formed?

Any clue how you do this?
0
6 years ago
#2
(Original post by HarrisonGCSE)
Its located on the OCR sample paper for 2015 if anyone is wondering. It states:

A student mixes 100cm3 of 0.200 mol dm-3 NaCl (Aq) with 100cm3 of 0.200 mol dm-3 (Na2)C(O3).

What is the total concentration of Na+ ions in the mixture formed?

Any clue how you do this?
Start by working out the amount, in mol, of Na+ in each sample.
0
6 years ago
#3
bump - I got 0.833... mol/dm3 when the answer is 0.3 :/
0
#4
Figured it out!

0.1 x 0.2 = 0.02 moles of NaCl. Therefore, there are 0.02 moles of Na+ in the NaCl
0.1 x 0.2 = 0.02 moles of Na2C03. Therefore, there are 0.02 moles of Na2 in the Na2CO3 meaning there are 0.04 moles of Na+ in Na2CO3.
0.02 + 0.04 = 0.06 moles
The total volume is 200cm3.
0.06/ 0.02dm3 = 0.3mol/dm3
6
6 years ago
#5
(Original post by HarrisonGCSE)
Figured it out!

0.1 x 0.2 = 0.02 moles of NaCl. Therefore, there are 0.02 moles of Na+ in the NaCl
0.1 x 0.2 = 0.02 moles of Na2C03. Therefore, there are 0.02 moles of Na2 in the Na2CO3 meaning there are 0.04 moles of Na+ in Na2CO3.
0.02 + 0.04 = 0.06 moles
The total volume is 200cm3.
0.06/ 0.02dm3 = 0.3mol/dm3
Thanks! I was stupid and when I saw there was 0.02 moles NaCl, I divided it by 2 to get 0.01 moles Na+ () and used the same technique for the other solution
1
6 years ago
#6
Can anyone help me with this question? Thanks
0
6 years ago
#7
(Original post by molly221)
Can anyone help me with this question? Thanks
Vanillin has extra polar group, as water is a polar solvent you can deduce the relative solubility from that (think about like dissolves like). As for the volatility consider comparing boiling points, think about which is likely to be higher bearing in mind that hydrogen bonding will increase the boiling point and then how that would relate to the compounds volatility.

Posted from TSR Mobile
0
6 years ago
#8
(Original post by HarrisonGCSE)
Figured it out!

0.1 x 0.2 = 0.02 moles of NaCl. Therefore, there are 0.02 moles of Na+ in the NaCl
0.1 x 0.2 = 0.02 moles of Na2C03. Therefore, there are 0.02 moles of Na2 in the Na2CO3 meaning there are 0.04 moles of Na+ in Na2CO3.
0.02 + 0.04 = 0.06 moles
The total volume is 200cm3.
0.06/ 0.02dm3 = 0.3mol/dm3
1) Why is the mole of Na+ ions in NaCl 0.02mol? Isn't that the number of moles for NaCl?
2) I have also worked out that Na2CO3 is 0.02 moles but again I don't get why Na+ would also be 0.02 mol
3) I understand that the total volume is 200 but why did you get 0.02dm3 from? That's not the volume though...

0
6 years ago
#9
(Original post by surina16)
Thanks! I was stupid and when I saw there was 0.02 moles NaCl, I divided it by 2 to get 0.01 moles Na+ () and used the same technique for the other solution
Hi, could you please explain to me how you solved this question? I still don't get it. Why is the mole of Na+ ions the same as the mole of NaCl? Thank you.
0
6 years ago
#10
(Original post by coconut64)
Hi, could you please explain to me how you solved this question? I still don't get it. Why is the mole of Na+ ions the same as the mole of NaCl? Thank you.
You need one mole of Na+ and one mole of Cl- to make one mole of NaCl, so it follows that if you have 0.02 moles of NaCl you will have 0.02 moles of Na. Remember that all the mole unit represents is the number of atoms/molecules.
0
6 years ago
#11
(Original post by coconut64)
Hi, could you please explain to me how you solved this question? I still don't get it. Why is the mole of Na+ ions the same as the mole of NaCl? Thank you.
If you have 1 mole of NaCl, it means that you have 1 mole of Na+ and 1 mole of Cl-, bonded together.
Therefore, if you have 0.02 moles of NaCl, you have 0.02 moles Na+ and 0.02 moles Cl-
0
6 years ago
#12
(Original post by surina16)
If you have 1 mole of NaCl, it means that you have 1 mole of Na+ and 1 mole of Cl-, bonded together.
Therefore, if you have 0.02 moles of NaCl, you have 0.02 moles Na+ and 0.02 moles Cl-
Oh okay. So if the mole of Na2Co3 is 0.4 mol, the mole of Na2 would be 0.8mol?
0
6 years ago
#13
(Original post by coconut64)
3) I understand that the total volume is 200 but why did you get 0.02dm3 from? That's not the volume though...

I think it's a typo and meant to be 0.2dm3. Which you get if you convert 200cm3 in to dm3. (10 cm in a dm, but as it's a volume it's 10^3 = 1000)

Posted from TSR Mobile
0
6 years ago
#14
(Original post by Rchilton)
I think it's a typo and meant to be 0.2dm3. Which you get if you convert 200cm3 in to dm3. (10 cm in a dm, but as it's a volume it's 10^3 = 1000)

Posted from TSR Mobile
Thanks for the help. Actually one more quick question. Say if the mole of Na2Co3 is 0.4mol, will 1 Na+ ion be 0.2 mol?
0
6 years ago
#15
(Original post by coconut64)
Oh okay. So if the mole of Na2Co3 is 0.4 mol, the mole of Na2 would be 0.2mol?
No I think you would have 0.4 mol Na2 which therefore means you would have 0.8 mol Na+
Spoiler:
Show
not 100% sure, but it seems to make sense logically
0
6 years ago
#16
(Original post by surina16)
No I think you would have 0.4 mol Na2 which therefore means you would have 0.2 mol Na
Spoiler:
Show
not 100% sure, but it seems to make sense logically

Really? But the OP mentioned that '0.1 x 0.2 = 0.02 moles of Na2C03. Therefore, there are 0.02 moles of Na2 in the Na2CO3 meaning there are 0.04 moles of Na+ in Na2CO3. ' So 0.02 mole for Na2. For all Na+ion, it will be 0.02*2. So if the mole of Na2CO3 is 0.4mole. Na2 ions will be 0.4 mole. All Na ions will be 0.8 right?
0
6 years ago
#17
(Original post by coconut64)
Really? But the OP mentioned that '0.1 x 0.2 = 0.02 moles of Na2C03. Therefore, there are 0.02 moles of Na2 in the Na2CO3 meaning there are 0.04 moles of Na+ in Na2CO3. ' So 0.02 mole for Na2. For all Na+ion, it will be 0.02*2. So if the mole of Na2CO3 is 0.4mole. Na2 ions will be 0.4 mole. All Na ions will be 0.8 right?
Oh yeah of course aha I meant to multiply by 2, not divide
Sorry for the confusion
0
6 years ago
#18
(Original post by surina16)
Oh yeah of course aha I meant to multiply by 2, not divide
Sorry for the confusion
Its okay, thanks for helping!
0
6 years ago
#19
plz can anyone help me I'm stuck.. Thanks

1.what is the molar its of a solution made by dissolving 49g of H2SO4, in water and diluting with water to 200ml total?

2. some compound has 14.3% C, 2.4%H, and 33.31% N,and has molecular mass of 126. what is the molecular formula of that compound.
0
4 years ago
#20
It is 0.01 x 0.2as when figuring out moles you need to convert the 100cm3 to dm3 and to do that you need to divide by 1000.if you do that you get 0.002 0.004 = 0.006and then 0.006/0.02 = 0.3(0.06 / 0.02 = 3)
0
X

new posts
Back
to top
Latest

Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

Poll

Join the discussion

Talking to current university students (12)
17.65%
Talking to peers going through the same thing (24)
35.29%
Speaking to student ambassadors from the universities (5)
7.35%
Speaking to staff members from universities (1)
1.47%
Using the personal statement builder, library or helper service (7)
10.29%
20.59%
Learning about/speaking to Student Finance England (2)
2.94%
Something else (tell us in the thread) (3)
4.41%