Problem: A solution is tested for pH and conductivity as pictured below:The solution contains one of the following substances: HCl, NaOH, NH4Cl, HCN, NH3, HF, or NaCN. If the solute concentration is about 1.0 M, what is the identity of the solute?

FREE Expert Solution

We can see that the reading is less than 7 so it means it is acidic.

However, it is also not that low so it must be a weak acid. 


We can narrow down our options to: 

 NH4Cl, HCN and HF


Make an ICE chart: 


Recall: 

Ka = productsreactantsKa = [A-][H3O+][HA]Ka = [x][x][1-x]


Calculate x using pH: 

[H3O+] = 10-pH[H3O+] = 10-4.6[H3O+] = 2.51×10-5 M


Calculate Ka:

Ka = [x][x][1-x]Ka = x2[1-x]Ka = (2.51×10-5)2[1-2.51×10-5]

K= 6.31 x10-10


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Problem Details

A solution is tested for pH and conductivity as pictured below:

The solution contains one of the following substances:

 HCl, NaOH, NH4Cl, HCN, NH3, HF, or NaCN. If the solute concentration is about 1.0 M, what is the identity of the solute?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the pH and pOH concept. You can view video lessons to learn pH and pOH. Or if you need more pH and pOH practice, you can also practice pH and pOH practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Stacey's class at University of Manitoba.

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition practice problems.