Question

The great French chemist Antoine Lavoisier discovered the Law of Conservation of Mass in part by doing a famous experiment in 1775. In this experiment Lavoisier found that mercury(II)oxide, when heated, decomposed into liquid mercury and an invisible and previously unknown substance: oxygen gas. D 1. Write a balanced chemical equation, including physical state symbols, for the decomposition of solid mercury(II)oxide (HgO) into liquid mercury and gaseous dioxygen 2. Suppose 87.0 mL of dioxygen gas are produced by this reaction, at a temperature of 100.0 °C and pressure of exactly 1 atm. Calculate the mass of mercury(II)oxide that must have reacted. Be sure your answer has the correct number of significant digits.

Answer 1

Write the equation for HgO(s) decomposition 2 H80(s)—>2 Hg(1)+3(8) Thus, 2 moles of HgO decomposes to give 2 mol of Hg(1) and 1 mol of 02(8). - - - - - - - - - - - - - - - - - - - - - - - - - - - - Calculate the number of moles of O, by using ideal gas equation. PV ņRT 1 atm x 0.087 L 0.0821 L atm/mol KX373.15 K = 0.00285 mol - - - - - - - - - - - - - - - - - - - - - 2 moles of HgO decomposes to give 1 mol of 0 (8) Moles of HgO=0.00285 mol O2x2 = 0.0057 mol Mass of HgO = 0.0057 mol x 216.59 g/mol =1.234563 g Thus, the mass of HgO = 1.23 g