The amount of solid KOH, in mol, that must be added to the solution to raise the pH to 13.0 would be
A - VCE - SSCE Chemistry - Question 15 - 2007 - Paper 1
Question 15
The amount of solid KOH, in mol, that must be added to the solution to raise the pH to 13.0 would be
A. 10^-13
B. 10^-12
C. 0.09
D. 0.10
Worked Solution & Example Answer:The amount of solid KOH, in mol, that must be added to the solution to raise the pH to 13.0 would be
A - VCE - SSCE Chemistry - Question 15 - 2007 - Paper 1
Step 1
Determine the pH and pOH relationship
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Answer
To find the pOH from the given pH value, we use the relationship:
extpOH=14−extpH
In this case:
extpOH=14−13=1
Step 2
Calculate the concentration of OH⁻ ions
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Answer
The concentration of hydroxide ions can be determined from the pOH using:
[OH−]=10−extpOH=10−1=0.1extM
Step 3
Calculate moles of KOH needed
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Answer
Assuming we are adding KOH to 1 liter of solution (as no volume is specified), the moles of KOH required can be directly taken from the concentration:
Thus, the number of moles needed is:
extmolesofKOH=0.1extmol
Step 4
Select the correct answer from the options
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Answer
From the provided options, the correct amount of solid KOH that must be added to achieve a pH of 13.0 is:
