University:
Ball State University
Course:
CHEM 111 | General Chemistry 1
Academic year:

2023
Views:

354

Pages:

3
Author:

michelle kh.

Law of Comparison of Volumes (Gay Lussac's Law) At first scientists discovered that hydrogen gas can react with oxygen gas to form water. The ratio of the volume of hydrogen and oxygen gas in the reaction is fixed, namely 2: 1. In 1808, Joseph Louis Gay Lussac conducted a similar experiment using various gases. He found that the ratio of the volumes of the gases in the reaction is always a simple integer. 2 volumes of hydrogen gas + 1 volume of oxygen gas 2 volumes of water vapor 1 volume of nitrogen gas + 3 volumes of hydrogen gas 2 volumes of gas ammonia 1 volume of hydrogen gas + 1 volume of chlorine gas 2 volumes of hydrogen chloride gas We can express Gay Lussac's experiments in the following reaction equation. 2 H2 (g) + O2 (g) H2 O(l) N2 (g) + 3 H2 (g) 2 NH3 (g) H2 (g) + Cl2 (g) 2 HCl(g) From this experiment, Gay Lussac formulated the volume ratio law (Gay Lussac's law): "At the same temperature and pressure, the volumes of the reacting gases and the volumes of the reacting gases are proportional as simple whole numbers." Gay's law of volumetric ratios. We can state Lussac as follows. "Comparison of the volume of gases according to the coefficient of each gas." For two gases (eg gas A and gas B) listed in one reaction equation, the relationship applies: Example 1. Ten mL of nitrogen gas (N2 ) and 15 mL of oxygen gas (O2 ) completely reacts to form 10 mL of NaOb gas . Determine the chemical formula of the NaO gas ! Answer: Coefficient ratio = volume ratio Coefficient N2 : O2 : NaOb = 10 : 15 : 10 = 2 : 3 : 2 2 N2 + 3 O2 2 Na Ob Since the number of atoms on the left-hand side and on the right-hand side are the same, the values for a and b can be found as follows. Number of N atoms left = Number of right N atoms 2 × 2 = 2a 4=2a a=2 Number of left O atoms= Number of right O atoms 3 × 2 = 2b 6 = 2b b=3 So, the chemical formula of the compound is N2O3 . Exercise 1 1. Five liters of acetylene gas is completely burned according to the following reaction equation. 2 C2 H2 (g) + 5 O2 (g) 4 CO2 (g) + 2 H2 O(g) At the same temperature and pressure, determine: a. volume of oxygen gas needed b. volume of carbon dioxide gas produced c. the volume of water produced 2. Ten liters of hydrogen bromide gas decompose as follows. 2 HBr(g) H2 (g) + Br2 (g) At the same temperature and pressure, determine the volume of hydrogen gas and bromine gas produced! 3. Five liters of gas N2 O5 decompose according to the following reaction. 2 N2 O5 (g) 2 N2 (g) + 5 O2 (g) At the same temperature and pressure, determine the volume of nitrogen gas and oxygen gas formed!