Given that the density of Hg(l) at 0°C is about 14 g mL-1, which of the following is closest to the — Stoichiometry Chemistry Question
Question
Given that the density of Hg(l) at 0°C is about 14 g mL-1, which of the following is closest to the volume of one mole of Hg(l) at this temperature?
0.070 mL
0.14 mL
1.4 mL
14 mL
28 mL
💡 Solution & Explanation
STEPS:
1. Identify the formula relating density, mass, and volume: Density () is defined as mass () divided by volume ():
Rearranging this formula to solve for volume yields:
2. Find the molar mass of Mercury (Hg): Liquid mercury () has a molar mass of approximately , which can be found on the periodic table included in the exam booklet. For a quick mental estimation on Section I—where calculators are not permitted—this value can be rounded to .
3. Calculate the mass of exactly one mole of :
4. Calculate the volume of one mole of : Substitute the estimated mass () and the given density () into our rearranged density equation:
This estimated volume is closest to 14 mL, which corresponds to Option D.
*
WHY_OTHERS_WRONG:
* A is incorrect: is obtained if a student mistakenly inverts the volume calculation and divides the density by the mass () instead of dividing the mass by the density.
* B is incorrect: represents a decimal place-value error during division, or is the result of using an incorrect value for the molar mass of mercury (such as its atomic number, 80).
* C is incorrect: is off by a factor of 10, which typically occurs due to a decimal-shifting mistake during long division (e.g., incorrectly writing the decimal point when dividing 200 by 14).
* E is incorrect: is double the correct volume, which could occur if a student mistakenly assumed that mercury exists as a diatomic molecule (such as ) under these conditions or made a multiplication error during division.