7. (a) Define (i) an acid, (ii) a base - Leaving Cert Chemistry - Question 7 - 2015
Question 7
7. (a) Define (i) an acid, (ii) a base.
(b) (i) Define pH.
(ii) Solutions A, B and C have pH values of 1, 6 and 4 respectively. Arrange the solutions in order of i... show full transcript
Worked Solution & Example Answer:7. (a) Define (i) an acid, (ii) a base - Leaving Cert Chemistry - Question 7 - 2015
Step 1
Define (i) an acid.
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Answer
An acid is a substance that gives hydrogen (hydronium) ions, H⁺ or H₃O⁺, in aqueous solution. It acts as a proton (hydrogen ion) donor.
Step 2
Define (ii) a base.
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Answer
A base is a substance that gives hydroxyl (hydroxide) ions, OH⁻, in aqueous solution. It acts as a proton (hydrogen ion) acceptor.
Step 3
Define pH.
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Answer
pH is defined as the negative logarithm of the concentration of hydrogen ions in a solution:
pH = - ext{log} rac{[H^+]}{[H_2O]}
Step 4
Arrange the solutions in order of increasing acidity.
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Answer
The order of solutions from least to most acidic is:
B (pH 6), C (pH 4), A (pH 1).
Step 5
Calculate the pH of a 0.03 M solution of sulfuric acid (H₂SO₄).
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Answer
Sulfuric acid is a strong acid that completely dissociates in solution. Therefore, the concentration of hydrogen ions, [H⁺], can be calculated as:
[H+]=0.03imes2=0.06M
To find the pH:
pH=−extlog[H+]=−extlog(0.06)=1.2
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