The mass of a $2.5 ext{ mL}$ solution (the density of the solution is $2.15 ext{ g/mL}$) in the correct si

Question

The mass of a $2.5 	ext{ mL}$ solution (the density of the solution is $2.15 	ext{ g/mL}$) in the correct significant figures is:

Accepted Answer

1. **Identify Data:**
   - Volume ($V$) = $2.5 	ext{ mL}$ (2 significant figures).
   - Density ($ho$) = $2.15 	ext{ g/mL}$ (3 significant figures).
2. **Calculate Mass:**
   $$ 	ext{Mass} = 	ext{Density} 	imes 	ext{Volume} $$
   $$ 	ext{Mass} = 2.15 	imes 2.5 = 5.375 	ext{ g} $$
3. **Apply Significant Figures Rule:**
   In multiplication, the final result should retain as many significant figures as the original number with the *least* significant figures [Class 11 Physics, Ch 1, Sec 1.3.1].
   - The term with the least significant figures is $2.5$ (2 sig figs).
4. **Round Off:**
   The result $5.375$ must be rounded to 2 significant figures. The digit to be dropped is 7 ($>5$), so the preceding digit (3) is raised by 1.
   $$ 5.375 ightarrow 5.4 	ext{ g} $$

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