Molarity to grams

  • Thread starter kremit
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  • #1
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Homework Statement


Calculate the mass (in grams) of KHP required to react completely with the NaOH in 35 mL of 0.100M NaOH.

KHP = KHC8H4O4(aq)
molar mass of "KHP"= 204.2 g/mol

Homework Equations



This is a double replacement reaction of the acid-base neutralization type. In other words the K will be replaced with Na and the product will have H2O in the mix.

The Attempt at a Solution



It wants KHP in grams.

g/m * m/L*

See this is where I get lost. I'm sure its something simple. Also m/l = M. Just to make sure, if I have the volume (L) and the Molarity (M) to get the moles, the only thing i have to do is multiple the volume by the molarity?
 

Answers and Replies

  • #2
Borek
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This is a double replacement reaction of the acid-base neutralization type. In other words the K will be replaced with Na and the product will have H2O in the mix.
You got it wrong, K won't be replaced by Na.

Try to write balanced reaction equation.

It wants KHP in grams.
Calculate moles first, then convert to grams. But you need balanced reaction equation first.

--
methods
 
  • #3
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thank you for the reply and groovy hair BTW. :cool: My mistake, it was the H. I had to look it over again.

KHC8H4O4(aq) + NaOH --> NaKC8H4O4 +H2O(l)

I looked over this a couple times and it looks balanced to me.

There is ...

1 Na -> 1 Na
1 K -> 1K
H+H4+H = 6 ->H4+H2= 6
C8 = C8
O4+O = 5 -> O4+O = 5

By chance is the problem:

mol NaOH x mol KHP/mol NaOH x g KHP/mol KHP ???
 
Last edited:
  • #4
Borek
Mentor
28,600
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Reaction is OK - you don't have to check separately if every element is balanced, note that C8H4O42- is present on both sides, it is not much different from other groups (like SO42-) that are almost always treated as a whole.

mol NaOH x mol KHP/mol NaOH x g KHP/mol KHP ???
Yes, that's OK - but it is obvious now, after you have checked what is stoichiometry of the reaction. 1 mole of KHP reacts with 1 mole of NaOH.

--
methods
 
  • #5
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Thank you. Last question would be about converting KHP to moles.

I don't understand how to make a conversion question for that.
 
  • #6
Borek
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28,600
3,078
Please elaborate, no idea what you mean.

You can easily calculate number of moles of NaOH, you know they react 1:1, so number ofmoles of KHP must be identical to number of moles of NaOH.

See also

http://www.titrations.info/titration-calculation
 
  • #7
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Calculate the amount(in moles) of KHP required to react completely with the NaOH in 35 mL of 0.100M NaOH.

This is what I was referring to.
 
  • #8
Borek
Mentor
28,600
3,078
Read my previous post, this is a simple stoichiometry.

Unless you have no idea what reation equation means. If so, please see how to read reaction equation.

--
methods
 
  • #9
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I am a beggining chemistry student and we have only had a couple lectures on stoichiometry and molarity. I will check out your site for further information.dziękuję
 

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