# urgent chemistry help needed!!!!!

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#1
Hi guys, I really need help with this question as i think it might come up in my mock on monday. This is the question
A copper sulfate solution contained 0.100 moles of copper sulfate dissolved
in 0.500 dm3 of water.
Calculate the mass of copper sulfate in 30.0 cm3 of this solution.
Relative formula mass (Mr): CuSO4 = 159.5
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3 months ago
#2
(Original post by lol9812)
Hi guys, I really need help with this question as i think it might come up in my mock on monday. This is the question
A copper sulfate solution contained 0.100 moles of copper sulfate dissolved
in 0.500 dm3 of water.
Calculate the mass of copper sulfate in 30.0 cm3 of this solution.
Relative formula mass (Mr): CuSO4 = 159.5

If 0.1 moles are present in 0.500 dm3, then how many moles would be present in 30 cm3?

This is normal ratio/proportion calculations that I’m sure you can do do make sure to convert the dm3 to cm3

Once you have your answer, use the formula of moles = mass / Molecular Mass to find the mass of Copper Sulfate in 30cm3
Last edited by qwert7890; 3 months ago
2
#3
(Original post by qwert7890)

If 0.1 moles are present in 0.500 dm3, then how many moles would be present in 30 cm3?

This is normal ratio/proportion calculations that I’m sure you can do do make sure to convert the dm3 to cm3

Once you have your answer, use the formula of moles = mass / Molecular Mass to find the mass of Copper Sulfate in 30cm3
Hi thankyou so much for your reply!! I think i have still got it wrong however and im really stressed I got 9.5 x 10^(-4)
I did this: 500dm3=500000cm3 so therefore i did 0.1 moles divided by 500000 to find the amount of moles present in 1cm3- i then multiplyied that by 30 and substituted it into the equation however my answer still doesnt look right
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3 months ago
#4
(Original post by lol9812)
Hi thankyou so much for your reply!! I think i have still got it wrong however and im really stressed I got 9.5 x 10^(-4)
I did this: 500dm3=500000cm3 so therefore i did 0.1 moles divided by 500000 to find the amount of moles present in 1cm3- i then multiplyied that by 30 and substituted it into the equation however my answer still doesnt look right
Your strategy is right, but is it 500dm3 or 0.500 dm3?

The equivalent of 0.500dm3 is equal to 500 cm3. So 0.1 moles in 500cm3, so 1cm3 will have 2x10^-4 moles.
Then multiply this by 30 to get number of moles of Copper Sulfate. Then multiply this by Mr of Copper Sulfate to get mass of copper Sulfate.

Cheers
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#5
(Original post by qwert7890)
Your strategy is right, but is it 500dm3 or 0.500 dm3?
The equivalent of 0.500dm3 is equal to 500 cm3. So 0.1 moles in 500cm3, so 1cm3 will have 2x10^-4 moles.
Then multiply this by 30 to get number of moles of Copper Sulfate. Then multiply this by Mr of Copper Sulfate to get mass of copper Sulfate.

Cheers
Thankyou so much I think i have the right answer now x
Last edited by lol9812; 3 months ago
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3 months ago
#6
(Original post by lol9812)
Thankyou so much I think i have the right answer now x
No problem what did you get
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#7
I got 0.957g x
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#8
(Original post by qwert7890)
No problem what did you get
I got 0.957g x
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3 months ago
#9
(Original post by lol9812)
I got 0.957g x
did you round it correctly?. to 3 s.f i got 0.956g
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#10
(Original post by 14nmathew)
did you round it correctly?. to 3 s.f i got 0.956g
I did 6x10^-3 x 159.5 which =0.957 so i would round it up to 0.96
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3 months ago
#11
(Original post by lol9812)
I did 6x10^-3 x 159.5 which =0.957 so i would round it up to 0.96
oh i misread the Mr as being 159.4 instead of 159.5. yh ur right with the answer
1
3 months ago
#12
(Original post by lol9812)
I did 6x10^-3 x 159.5 which =0.957 so i would round it up to 0.96
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#13
(Original post by qwert7890)
Thankyou so much for helping !!
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2 months ago
#14
you guys are amazing
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2 months ago
#15
i got 9.57g
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2 months ago
#16
(Original post by stormtd_)
i got 9.57g
Post your working! You’ve multiplied by x100 at some step mistakenly (or missed out on dividing by 100)
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2 months ago
#17
converted 30.0 cm3 ----- 0.03 dm3
concentration in mol/dm3 = amount of solute in mol / volume in dm3
0.100/0.500 = 0.2 mol = concentration of copper sulfate
0.2 x 0.003 = 0.06mol
0.06 x 159.5 = 9.57
0
2 months ago
#18
(Original post by qwert7890)
Post your working! You’ve multiplied by x100 at some step mistakenly (or missed out on dividing by 100)
converted 30.0 cm3 ----- 0.03 dm3
concentration in mol/dm3 = amount of solute in mol / volume in dm3
0.100/0.500 = 0.2 mol = concentration of copper sulfate
0.2 x 0.003 = 0.06mol
0.06 x 159.5 = 9.57

hi can you check what i have done wrong?
0
2 months ago
#19
(Original post by stormtd_)
converted 30.0 cm3 ----- 0.03 dm3
concentration in mol/dm3 = amount of solute in mol / volume in dm3
0.100/0.500 = 0.2 mol = concentration of copper sulfate
0.2 x 0.003 = 0.06mol
0.06 x 159.5 = 9.57

hi can you check what i have done wrong?
You did 0.2 x 0.003 it is meant to be 0.2 x 0.03
also how did you get 0.06 mol for it you would get 6 x 10^-4 mol
1
2 months ago
#20
(Original post by !AXEL!)
You did 0.2 x 0.003 it is meant to be 0.2 x 0.03
also how did you get 0.06 mol for it you would get 6 x 10^-4 mol
ahh i just realized what ive done wrong! thank you so much
0
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