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Topic: Concentration of solutions  (Read 8441 times)

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Offline jray

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Concentration of solutions
« on: January 07, 2008, 09:51:57 AM »
Good day everybody.
First off all, i'm not very good at chemistry and i don't know how to solve this problem:
How many litres of 10% HCL solution (d=1.07g/cm3) it is possible to neutralise with 16 kg of NaOH?
I know it looks easy for most of you, but i couldn't solve it.

Offline AWK

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Re: Concentration of solutions
« Reply #1 on: January 07, 2008, 10:11:50 AM »
Start from a balanced equation of neutralization reaction
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Offline jray

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Re: Concentration of solutions
« Reply #2 on: January 07, 2008, 10:19:47 AM »
HCl(aq) + NaOH -> H2O(l) + NaCl(aq)

Offline Arkcon

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Re: Concentration of solutions
« Reply #3 on: January 07, 2008, 10:31:55 AM »
Well done, now you a balanced equation.  The units used in chemistry for a balanced equation is moles.  You now have to convert % HCl and kg of NaOH to moles.  It's just like converting imperial units to metric. (Hint: why'd they give you density of HCl? What are it's units, and how do they relate to moles?)
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline jray

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Re: Concentration of solutions
« Reply #4 on: January 07, 2008, 11:53:01 AM »
M(NaOH) = 16000 x 1mol/40 = 400 moles

10g HCl solute - 100g solution
x g - 1070 g     
-----
x=107g/l

M(HCl)=107/36=2.97mol/l

Correct me if i'm wrong

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Re: Concentration of solutions
« Reply #5 on: January 07, 2008, 12:09:49 PM »
M(NaOH) = 16000 x 1mol/40 = 400 moles

Thats OK.

Quote
10g HCl solute - 100g solution
x g - 1070 g     
-----
x=107g/l

M(HCl)=107/36=2.97mol/l

Correct me if i'm wrong

Hard to say - you have correctly calculated amount of HCl in 1L of solution - but that's not what the questions asks for, although it can be a convenient intermediary result.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info

Offline jray

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Re: Concentration of solutions
« Reply #6 on: January 07, 2008, 12:12:34 PM »
So what i need to do next?

Offline AWK

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Re: Concentration of solutions
« Reply #7 on: January 07, 2008, 12:49:51 PM »
Stoichiometry of reaction says you 1 mole HCl react with 1 mole of NaOH. Hence you need 400 moles of HCl.
Now you can calculate volume of HCl. (2.97 mole in 1 liter)
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Offline jray

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Re: Concentration of solutions
« Reply #8 on: January 07, 2008, 01:25:12 PM »
Stoichiometry of reaction says you 1 mole HCl react with 1 mole of NaOH. Hence you need 400 moles of HCl.
Now you can calculate volume of HCl. (2.97 mole in 1 liter)
So just a simple division (400/2.97) or I misunderstood something?
« Last Edit: January 07, 2008, 02:29:19 PM by jray »

Offline AWK

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Re: Concentration of solutions
« Reply #9 on: January 08, 2008, 01:04:59 AM »
Just a simple division!

400 [mol] / 2,97 [mol/L] = xxx [L]
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Offline jray

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Re: Concentration of solutions
« Reply #10 on: January 08, 2008, 04:29:24 AM »
So this is final answer? ??? Hope it is ok, thank you for the help then

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