Question

question 5: acids, bases and indicators

a) state whether each substance is strongly or weakly acidic, neutral or strongly or weakly alkaline.
\

$$\begin{tabular}{|c|c|} \\hline ph & classification \\\\ \\hline 5 & \\\\ \\hline 11 & \\\\ \\hline 7 & \\\\ \\hline 2 & \\\\ \\hline \\end{tabular}$$

b) universal indicator colours
complete the table.
\

$$\begin{tabular}{|l|l|} \\hline solution type & expected colour \\\\ \\hline magnesium hydroxide & \\\\ \\hline sulfuric acid + sodium hydroxide & \\\\ \\hline nitric acid & \\\\ \\hline \\end{tabular}$$

c) litmus paper
what colour change would occur if:

1. litmus paper is placed in sodium hydroxide?
2. litmus paper is placed in sulfuric acid?

Explanation:

Analyze pH classifications

The pH scale measures acidity or alkalinity:

• pH 1–2: Strongly acidic
• pH 3–6: Weakly acidic
• pH 7: Neutral
• pH 8–11: Weakly alkaline
• pH 12–14: Strongly alkaline

Applying this to the given values:

• pH 5 is weakly acidic.
• pH 11 is weakly alkaline.
• pH 7 is neutral.
• pH 2 is strongly acidic.

Determine Universal Indicator colors

Universal indicator changes color based on pH:

• Nitric acid is a strong acid (pH ~1–2), turning red.
• Sulfuric acid + Sodium Hydroxide is a neutralization reaction yielding a neutral salt solution (pH ~7), turning green.
• Magnesium hydroxide is a weak base (pH ~10), turning blue.

Determine Litmus paper color changes

Litmus paper is an indicator:

• In basic/alkaline solutions (like sodium hydroxide), litmus turns blue.
• In acidic solutions (like sulfuric acid), litmus turns red.

Answer:

Question 5a

pH	Classification
11	Weakly alkaline
7	Neutral
2	Strongly acidic

Question 5b

Solution Type	Expected Colour
Sulfuric acid + Sodium Hydroxide	Green
Magnesium hydroxide	Blue

Question 5c

1. Blue
2. Red