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
Calculate the hydroxide ion concentration for pH 13.0
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Answer
To find the concentration of hydroxide ions, we first need to convert the pH to pOH:
pOH=14−pH=14−13=1
Next, we can calculate the hydroxide ion concentration ([OH−]) using the formula:
[OH−]=10−pOH=10−1
Thus, [OH−]=0.1mol/L.
Step 2
Determine the amount of KOH needed to achieve this concentration
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Answer
Since KOH is a strong base, it fully dissociates in solution to provide hydroxide ions. To raise the hydroxide concentration to 0.1mol/L, we can assume that the volume of the solution remains constant.
Using the formula:
n=CimesV
where:
n = moles of KOH needed
C = desired concentration of OH− = 0.1mol/L
V = volume of solution in liters
As there is no specified volume, assuming we are working with 1L for simplicity:
n=0.1mol/L×1L=0.1mol
Therefore, the amount of solid KOH needed is 0.1mol.
