The mass of a piece of weighing paper is . The mass of a solid substance along with the paper is . I — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question
Question
The mass of a piece of weighing paper is $0.02 \text{ g}$. The mass of a solid substance along with the paper is $20.036 \text{ g}$. If the volume of the solid is $2.16 \text{ cm}^3$, how many significant figures should be used to report the final density of the solid?
💡 Solution & Explanation
Step 1: Find the mass of the solid by subtraction: $20.036 \text{ g} - 0.02 \text{ g}$. Based on the subtraction rule, the result must be rounded to two decimal places (due to $0.02$), giving $20.02 \text{ g}$. This value now has 4 significant figures. Step 2: Calculate density = Mass / Volume = $20.02 \text{ g} / 2.16 \text{ cm}^3$. The mass has 4 sig figs and volume has 3 sig figs. By the division rule, the final density must be reported to 3 significant figures.