Leaving Cert Chemistry Acids, Bases & PH: 7. (a) Define (i) an acid, (ii)

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:

$[H^+] = 0.03 imes 2 = 0.06 M$

To find the pH:

$pH = - ext{log} [H^+] = - ext{log}(0.06) = 1.2$

7. (a) Define (i) an acid, (ii) a base - Leaving Cert Chemistry - Question 7 - 2015

Worked Solution & Example Answer:7. (a) Define (i) an acid, (ii) a base - Leaving Cert Chemistry - Question 7 - 2015

Define (i) an acid.

Define (ii) a base.

Define pH.

Arrange the solutions in order of increasing acidity.

Calculate the pH of a 0.03 M solution of sulfuric acid (H₂SO₄).

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