Plan an investigation to find out which of these calcium compounds neutralizes acid most effectively.

Here is the plan for the investigation:

a) Aim of the experiment:
To compare the effectiveness of calcium carbonate ($\text{CaCO}_3$), calcium hydroxide ($\text{Ca(OH)}_2$), and calcium oxide ($\text{CaO}$) in neutralizing dilute hydrochloric acid ($\text{HCl}$).

b) Hypothesis:
Calcium oxide ($\text{CaO}$) will be the most effective neutralizer due to its strong basicity and reactivity, followed by calcium hydroxide ($\text{Ca(OH)}_2$), and then calcium carbonate ($\text{CaCO}_3$).

c) Variables of the experiment:

• Independent variable: The type of calcium compound used ($\text{CaCO}_3$, $\text{Ca(OH)}_2$, $\text{CaO}$).
• Dependent variable: The change in pH of the acid solution after adding the calcium compound.
• Controlled variables: Mass of calcium compound, initial volume and concentration of dilute $\text{HCl}$, temperature, stirring rate, reaction time.

d) List of the apparatus:

• Three beakers or conical flasks (e.g., 100 mL)
• Measuring cylinder (e.g., 50 mL)
• Electronic balance
• Spatula
• Stirring rods
• pH meter or universal indicator paper
• Dropper
• Wash bottle with distilled water
• Dilute hydrochloric acid (e.g., 0.1 M $\text{HCl}$)
• Calcium carbonate ($\text{CaCO}_3$) powder
• Calcium hydroxide ($\text{Ca(OH)}_2$) powder
• Calcium oxide ($\text{CaO}$) powder

e) Procedure of the experiment:

1. Measure 50 mL of dilute $\text{HCl}$ into each of the three separate beakers.
2. Measure the initial pH of the $\text{HCl}$ in each beaker using a pH meter and record the values.
3. Weigh out 1.0 g of calcium carbonate ($\text{CaCO}_3$), 1.0 g of calcium hydroxide ($\text{Ca(OH)}_2$), and 1.0 g of calcium oxide ($\text{CaO}$) separately.
4. Add 1.0 g of $\text{CaCO}_3$ to the first beaker, 1.0 g of $\text{Ca(OH)}_2$ to the second, and 1.0 g of $\text{CaO}$ to the third.
5. Stir each mixture continuously for a fixed time (e.g., 5 minutes) to ensure complete reaction.
6. After the reaction time, measure the final pH of the solution in each beaker and record the values.
7. Calculate the change in pH for each compound.

f) Tabulation of data:
A table should be prepared to record the results:

Calcium Compound	Initial pH of HCl	Final pH of Solution	Change in pH
$\text{CaCO}_3$
$\text{Ca(OH)}_2$
$\text{CaO}$

g) Conclusion from the investigation:
Based on the tabulated data, the calcium compound that causes the largest increase in pH (or brings the pH closest to 7) is the most effective in neutralizing the acid.