Significant Figures in Average Titre Volume Calculation

To find the number of significant figures in the average titre value, we follow the rules for significant figures during mathematical operations (addition and division).

Step 1: Calculate the sum of the titre values
$\text{Sum} = 25.2\text{ mL} + 25.25\text{ mL} + 25.0\text{ mL} = 75.45\text{ mL}$

In addition, the result must be rounded off to the same number of decimal places as the value with the fewest decimal places:

• $25.2\text{ mL}$ has $1$ decimal place.
• $25.25\text{ mL}$ has $2$ decimal places.
• $25.0\text{ mL}$ has $1$ decimal place.

The fewest number of decimal places is $1$ (tenths place). Thus, the sum is reported as $75.5\text{ mL}$, which contains $3$ significant figures.

Step 2: Calculate the average value
$\text{Average titre value} = \frac{75.45\text{ mL}}{3} = 25.15\text{ mL}$

Here, the number $3$ is an exact count (exact number) and has an infinite number of significant figures. Therefore, the division result is limited by the number of significant figures/decimal places of the numerator.

Rounding $25.15\text{ mL}$ to $1$ decimal place (matching the precision of $1$ decimal place from the sum) gives:
$\text{Average titre value} = 25.2\text{ mL}$

Step 3: Determine the number of significant figures
The final value $25.2\text{ mL}$ has $3$ significant figures.