Chem 115 Unit 3

Law of Conservation Of Matter

Matter cannot either be gained or lost in a chemical reaction

Combination (synthesis)

A+B→ AB

Decomposition

AB→A+B

Single Displacement

A+BC→AC+B

Double Displacement

AB+CD→AD+BC

Combustion

C_xH_y+O_2→CO_2+H_2O

A combustion reaction is a reaction with Oxygen (O2), Usually generates heat and light

Stiochiometry

The study of the numerical relationships between chemical quantities in a chemical reaction

Guidelines for determining stoichiometric calculations

1. If you are not given it, write and balance the chemical equation

2. Start dimensional analysis with the quantity of substance that you are given. If you are given a mass unit other than grams, convert to grams using necessary conversion factors

3. Convert form grams of substance X to moles of substance X using the substances molar mass. Molar mass for an element is on the P.T. but the molar mass of a compound must be determined

4. Convert from moles of substance X to moles of substance Y, using the coefficients from the balanced chemical equation to create a molar mass ratio conversion factor

5. convert from moles of substance Y to grams of substance Y, using the substance’s molar mass

6. if necessary, convert from grams of substance Y to the desired unit

7. Calculate the answer and report using the correct number of sig figs

Limiting reactant

the reactant that is completely consumed in a chemical reaction and limits the amount of product

Reactant in excess

any reactant that occurs in a quantity greater than is required to completely react with the limiting reactant

Theoretical yield

amount of product that can be made in a chemical reaction based on the amount of limiting reactant

actual yield

the amount of product actually produced by a chemical reaction

Percent yield

actual yield/theoretical yield x 100%

How to determine Limiting reactant

• calculate the possible yields of the product using EACH REACTANT, then compare the two

• The lesser amount is the theoretical yield, and the reactant that produced the lesser amount is the limiting reactant