Question: 68: The density of the solution is 2.15 \mathrm{~g} \mathrm{~mL}^{-1}, then mass of 2.5 mL solution in correct significant figures is
(1) 5375 \times 10^{-3} \mathrm{~g}
(2) 5.4 g
(3) 5.38 g
(4) 53.75 g
Answer: Option (2)
Explanation:
Mass of a solution is calculated using the relation:
\text{mass} = \text{density} \times \text{volume}Given density is 2.15 \mathrm{~g\,mL^{-1}} and volume is 2.5 \mathrm{~mL}.
Substituting the values:
\text{mass} = 2.15 \times 2.5 = 5.375 \mathrm{~g}Now, applying the rules of significant figures.
Density has 3 significant figures and volume has 2 significant figures.
Therefore, the final answer should be reported with 2 significant figures.
Rounding 5.375 to 2 significant figures gives:
5.4 \mathrm{~g}Hence, the mass of the solution is 5.4 g.
Therefore, option (2) is correct.