At 25°C, the pH of 0.0050 M Ba(OH)₂ is:
A - VCE - SSCE Chemistry - Question 3 - 2003 - Paper 1
Question 3
At 25°C, the pH of 0.0050 M Ba(OH)₂ is:
A. 2.0
B. 2.3
C. 11.7
D. 12.0
Worked Solution & Example Answer:At 25°C, the pH of 0.0050 M Ba(OH)₂ is:
A - VCE - SSCE Chemistry - Question 3 - 2003 - Paper 1
Step 1
Calculate the concentration of hydroxide ions [OH⁻]
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Answer
Barium hydroxide, Ba(OH)₂, dissociates in water according to the following equation:
Ba(OH)2→Ba2++2OH−
From this equation, it is clear that one mole of Ba(OH)₂ produces two moles of hydroxide ions. Thus, the concentration of hydroxide ions in a 0.0050 M Ba(OH)₂ solution is:
[OH−]=2×0.0050=0.0100M
Step 2
Calculate the pOH
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Answer
The pOH can be calculated using the formula:
pOH=−log[OH−]
Substituting the [OH⁻] value we found:
pOH=−log(0.0100)=2.00
Step 3
Calculate the pH
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Answer
Using the relationship between pH and pOH, we can find the pH:
pH+pOH=14
Substituting the value of pOH:
pH=14−2.00=12.00
Step 4
Select the correct answer
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Answer
Based on the calculated pH, the correct answer is D. 12.0.
