Question

question 6: investigating ph
a student measures the ph of four liquids.
\

$$\begin{array}{|l|c|} \\hline \\text{liquid} & \\text{ph} \\\\ \\hline \\text{lemon juice} & 2 \\\\ \\hline \\text{milk} & 6 \\\\ \\hline \\text{water} & 7 \\\\ \\hline \\text{soap solution} & 11 \\\\ \\hline \\end{array}$$

a) describe one way to make lemon juice less acidic, increase ph.
b) describe one way to make soap solution less alkaline, decrease ph.

question 7:
a student mixes nitric acid with potassium hydroxide.
a) what type of reaction is taking place?
b) complete the word equation.
nitric acid + potassium hydroxide \
ightarrow \text{______________} + \text{______________}
\

$$\begin{array}{|l|l|} \\hline \\text{name the ions that cause the nitric} & \\text{name the ions that cause the} \\\\ \\text{acid to change the universal indicator:} & \\text{potassium hydroxide to change the} \\\\ & \\text{universal indicator:} \\\\ \\hline \\end{array}$$

c) explain what happens to the ions during this reaction.

Explanation:

Analyze pH adjustments

Using the pH Scale knowledge point:
To make lemon juice (\(\text{pH } 2\)) less acidic (increase pH), add water to dilute it, or add an alkaline substance.
To make soap solution (\(\text{pH } 11\)) less alkaline (decrease pH), add water to dilute it, or add an acidic substance.

Identify reaction type

Using the Neutralization Reactions knowledge point:
Mixing nitric acid (an acid) with potassium hydroxide (an alkali) is a neutralization reaction.

Complete word equation

Using the Neutralization Reactions knowledge point:
An acid and a metal hydroxide react to produce a salt and water:

$$ \text{Nitric Acid} + \text{Potassium Hydroxide} ightarrow \text{Potassium Nitrate} + \text{Water} $$

Identify indicator-changing ions

Acids release hydrogen ions (\(\text{H}^+\)) which turn universal indicator red/orange.
Alkalis release hydroxide ions (\(\text{OH}^-\)) which turn universal indicator blue/purple.

Describe ionic reaction

During neutralization, hydrogen ions (\(\text{H}^+\)) from the acid react with hydroxide ions (\(\text{OH}^-\)) from the alkali to form neutral water molecules (\(\text{H}_2\text{O}\)).

Answer:

Question 6

a) Add water to dilute the lemon juice, or add a small amount of an alkaline substance.
b) Add water to dilute the soap solution, or add a small amount of an acidic substance.

Question 7

a) Neutralization.
b) Nitric Acid + Potassium Hydroxide \(
ightarrow\) Potassium Nitrate + Water.
c)

• Ions causing Nitric acid to change universal indicator: Hydrogen ions / \(\text{H}^+\)
• Ions causing Potassium Hydroxide to change universal indicator: Hydroxide ions / \(\text{OH}^-\)
• What happens to the ions: The hydrogen ions (\(\text{H}^+\)) and hydroxide ions (\(\text{OH}^-\)) react together to form neutral water molecules (\(\text{H}_2\text{O}\)).