# Reaction Stoichiometry and Gases

This article is part of the ChemHelp Tutoring Wiki |

In chemistry, stoichiometry deals with the quantitative relationships that exist among the reactants and products in chemical reactions.

## Contents

### Summary

Molar Mass: Found by adding together the molar masses of all of its elements.

Empirical Formula: Contains the smallest set of whole-number subscripts that give relative amounts of constituent atoms.

Molecular Formula: A chemical formula that gives the exact number of different atoms of an element in a molecule.

Law of Conservation of Mass: In every chemical operation an equal quantity of matter exists before and after the operation.

Stoichiometry: Is the use of chemical equations to calculate quantities of substances that take part in chemical reactions.

Stoichiometry Quantities:The exact amounts of reactants and products predicted by the balanced equations.

Limiting Reactant: Is the reactant that runs out first, based on the stoichiometric ratio of all the reactants.

Theoretical Yield: The amount of product predicted by stoichiometry.

Actual Yield: The amount actually obtained.

Percent Yield: The percentage of the theoretical amount that is actually obtained:

Combustion Analysis: A weighted sample of a compound is burned in a stream of oxygen gas; after combustion, all the carbon atoms in the sample are found in the and all the H atoms are in the .

Percent composition: Percent of a substance contained within a molecule.

## Gas Laws

### Boyles' Law

Describe the reactionship between the volume and the pressure of a gas when temperature and amount are constant.If you have a container and derease the volume of the container, the pressure of the gas increases because the number of collisions of gas particles with the container's inside walls increase.

Methematically, this is an inverse realationship, so the product of the pressure and volume is a constant: PV = k

### Charles' Law

describe the volume and temperature relationship of a gass when the pressure and amount are constant. If a sample of gas is heated,the volume must increase for the pressure to remain constant. Mathematically, this law can be expressed as follows: V/T = k

### Gay Lussac's Law

Describe the realationship between the pressure of a gas and its Kelvin temperature if the volume and amount are held constant. As the gas is heated, the particle move with greater kinetic energy, striking the inside walls of the container more often and with greater force. This causes the pressure of the gass to increase. The realtionship between the Kelvin temperature and the pressure is a direct one: P/T = k

### Combined gas Law

Combine Boyle's charles' and Gay-Lussac's Laws. The combined gas law can be expressed as (P1 V1)/T1 = (P2 V2)/T2

### Avogadro's law

If a container is kept at constant pressure and temperature, and you increase the number of gas particles in that container, the volume will have to increase in order to keep the pressure of gas particles in that container, the volume will have to increase in order to keep the pressure constant.

### Dalton's Law of partial Pressure

in a mixture of gas (A + B+ C) the total pressure is simpley the sum of the partial pressure. The partial pressure of gas A can be expressed as Pa= (P total) (Xa)

### Gramham's Law of Diffusion and Effusion

the relationship of the speed of gas diffusion (mixing of gas due to their kinetic energy) or effusion (movement of a gas through a tiny opening) and the gasses molecular mass. The lighter the gas, the faster is its rate of effusion. NOrmally, this is set up as the comparision of the effusion rates of two gasses and the specific mathematicall relationship is : r1 / r2 = (M2/M1) ^ (1/2)