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# Chemistry Mass and Concentration Help ASAP watch

1. a) The concentration of a solution of 265 moles of NaOH dissolved in 1dm^3 of water

SO if moles/volume = concentration is the answer 265/1=265???

b) The mass of H2 SO4 that should be dissolved in 1dm^3 of water to make a solution of concentration 0.72mol dm-3

mol= vol*conc so 1*0.72= 0.72 and g=mr*mol so 98*0.72=70.56??

dont think im doing any of this right tbh...
2. (Original post by stressed16)
a) The concentration of a solution of 265 moles of NaOH dissolved in 1dm^3 of water

SO if moles/volume = concentration is the answer 265/1=265???

b) The mass of H2 SO4 that should be dissolved in 1dm^3 of water to make a solution of concentration 0.72mol dm-3

mol= vol*conc so 1*0.72= 0.72 and g=mr*mol so 98*0.72=70.56??

dont think im doing any of this right tbh...
3. (Original post by RDB1826)
Really? Because these questions are for a suduko challenge and my numbers aren't matching up... also I'm getting 0 as digits when the numbers are from 1 to 9 which leads me to believe im doing something wrong?
4. (Original post by stressed16)
Really? Because these questions are for a suduko challenge and my numbers aren't matching up... also I'm getting 0 as digits when the numbers are from 1 to 9 which leads me to believe im doing something wrong?
Oh right, because from what you've described your answers seem fine, could you write out the exact questions out word for word?

Also do they want the concentration in mol/dm^3 or g/dm^3?

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5. (Original post by RDB1826)
Oh right, because from what you've described your answers seem fine, could you write out the exact questions out word for word?

Also do they want the concentration in mol/dm^3 or g/dm^3?

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6. I think theres something missing from this question
7. (Original post by #jussiesoSMART)
I think theres something missing from this question

??????
8. (Original post by stressed16)
We know that the mass one should be 71g not 70.56 because it says you must give the answer to 2sf. So that ones ok.

Edit- just realised you've penciled in 71!

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9. Lemme get back to you about the first one, still can't seem to get a different answer...

Tbh I still think your top left box is right , with a 4 in the middle as you've done
10. (Original post by RDB1826)
Lemme get back to to about the first one, still can't seem to get a different answer...
Think i've got it now - my calculations were fine it was just significant number issues lol cheers
11. (Original post by RDB1826)
Lemme get back to you about the first one, still can't seem to get a different answer...

Tbh I still think your top left box is right , with a 4 in the middle as you've done
I actually do need help with g) if that's something you can help me figure out?
12. (Original post by stressed16)
I actually do need help with g) if that's something you can help me figure out?
You'll need to times your 1.582dm^3 (remember need to convert to dm^3) by your concentration of 2mol/dm^3. This will give you the moles. All you need to do then is times these moles by the Mr of the iron complex to give you the mass required. Then give to 3sf.

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Updated: November 13, 2015
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