A lab group decides to test a manufacturer's claim that an antacid product contains 200 mg of sodium bicarbonate. Each tablet was placed into an Erlenmeyer flask, 10.00 mL of water was added, and then the tablets were crushed. An indicator was added to each flask, and then each sample was titrated with [tex]$0.200 \, \text{mol/L}$[/tex] hydrochloric acid. The titration evidence was collected in Table 8.3.

\begin{tabular}{|c|c|c|c|c|}
\hline
Trial & 1 & 2 & 3 & 4 \\
\hline
Final burette reading (mL) & 11.6 & 21.7 & 31.7 & 41.8 \\
\hline
Initial burette reading (mL) & 0.6 & 11.6 & 21.7 & 31.7 \\
\hline
Volume of [tex]$\text{HCl (aq)}$[/tex] added (mL) & 11.0 & 10.1 & 10.0 & 10.1 \\
\hline
Indicator color & red & orange & orange & orange \\
\hline
\end{tabular}

Question 12 (3 points)

Use Scenario 8.3 to answer the following question.

The calculated mass of sodium bicarbonate in the antacid tablet is:



Answer :

Let's go through the steps to calculate the mass of sodium bicarbonate in the antacid tablets.

### 1. Determine the Volume of HCl Added

We begin by finding the volume of hydrochloric acid (HCl) added for each trial. This is calculated by subtracting the initial burette reading from the final burette reading for each trial.

- Trial 1: [tex]\(11.6 \, mL - 0.6 \, mL = 11.0 \, mL\)[/tex]
- Trial 2: [tex]\(21.7 \, mL - 11.6 \, mL = 10.1 \, mL\)[/tex]
- Trial 3: [tex]\(31.7 \, mL - 21.7 \, mL = 10.0 \, mL\)[/tex]
- Trial 4: [tex]\(41.8 \, mL - 31.7 \, mL = 10.1 \, mL\)[/tex]

So, the volumes of HCl added are:
[tex]\[ [11.0 \, mL, 10.1 \, mL, 10.0 \, mL, 10.1 \, mL] \][/tex]

### 2. Calculate the Moles of HCl Added

Next, we use the concentration of HCl to find the number of moles of HCl added in each trial. The concentration of HCl is given as [tex]\(0.200 \, mol/L\)[/tex].

To convert from mL to L and then find the moles, we use the formula:
[tex]\[ \text{Moles of HCl} = \text{Volume of HCl} \times \text{Concentration of HCl} \][/tex]

- Trial 1: [tex]\(11.0 \, mL \times 0.200 \, mol/L \times \frac{1 \, L}{1000 \, mL} = 0.0022 \, mol\)[/tex]
- Trial 2: [tex]\(10.1 \, mL \times 0.200 \, mol/L \times \frac{1 \, L}{1000 \, mL} = 0.00202 \, mol\)[/tex]
- Trial 3: [tex]\(10.0 \, mL \times 0.200 \, mol/L \times \frac{1 \, L}{1000 \, mL} = 0.0020 \, mol\)[/tex]
- Trial 4: [tex]\(10.1 \, mL \times 0.200 \, mol/L \times \frac{1 \, L}{1000 \, mL} = 0.00202 \, mol\)[/tex]

So, the moles of HCl added are:
[tex]\[ [0.0022 \, mol, 0.00202 \, mol, 0.0020 \, mol, 0.00202 \, mol] \][/tex]

### 3. Determine the Moles of NaHCO₃

Given that sodium bicarbonate (NaHCO₃) reacts in a 1:1 molar ratio with HCl, the moles of NaHCO₃ will be equal to the moles of HCl added.

So, the moles of NaHCO₃ are:
[tex]\[ [0.0022 \, mol, 0.00202 \, mol, 0.0020 \, mol, 0.00202 \, mol] \][/tex]

### 4. Calculate the Mass of NaHCO₃

To find the mass of sodium bicarbonate in each trial, we use the molar mass of NaHCO₃, which is [tex]\(84.007 \, g/mol\)[/tex].

[tex]\[ \text{Mass of NaHCO₃} = \text{Moles of NaHCO₃} \times \text{Molar mass of NaHCO₃} \][/tex]

Converting the mass to mg by multiplying by [tex]\(1000 \, mg/g\)[/tex],

- Trial 1: [tex]\(0.0022 \, mol \times 84.007 \, g/mol \times 1000 \, mg/g = 184.8154 \, mg\)[/tex]
- Trial 2: [tex]\(0.00202 \, mol \times 84.007 \, g/mol \times 1000 \, mg/g = 169.69414 \, mg\)[/tex]
- Trial 3: [tex]\(0.0020 \, mol \times 84.007 \, g/mol \times 1000 \, mg/g = 168.014 \, mg\)[/tex]
- Trial 4: [tex]\(0.00202 \, mol \times 84.007 \, g/mol \times 1000 \, mg/g = 169.69414 \, mg\)[/tex]

So, the masses of NaHCO₃ in each tablet are:
[tex]\[ [184.8154 \, mg, 169.69414 \, mg, 168.014 \, mg, 169.69414 \, mg] \][/tex]

### Conclusion

The calculated masses of sodium bicarbonate in the antacid tablets for the trials are:

[tex]\[ \boxed{184.8154 \, mg, 169.69414 \, mg, 168.014 \, mg, 169.69414 \, mg} \][/tex]

Based on the calculated values, the manufacturer's claim that each antacid tablet contains 200 mg of sodium bicarbonate does not hold true for these trials, as the average mass is significantly lower.