Stoichiometry

Question 1

What does a balanced chemical equation tell you

Answer 1

A balanced chemical equation tells you what amounts of reactants to mix and what amount of a product to expect

Question 2

When you know the quantity of a substance in the reaction what can you calculate

Answer 2

You can calculate the quantity of any other substance consumed or created in the reaction
Quantity = Amount of a substance in grams or moles

Question 3

Define stoichiometry

Answer 3

The calculation of quantities in chemical reactions is a subject of chemistry called stoichiometry

Question 4

What does stoichiometry do

Answer 4

Allows chemists to tally, or keep track, of the amounts of reactants and products each reaction uses and makes

Question 5

What quantities can a balanced chemical equation be interpreted by

Answer 5

Number of atoms
Number of moles
Number of molecules
Mass
Volume

Question 6

Number of atoms and an example

Answer 6

Number and types of atoms are not changed throughout a chemical reaction
Ex: N2 + 3H2 = 2NH3 (2 nitrogen atoms, 6 hydrogen atoms)

Question 7

Number of molecules and an example

Answer 7

The same amount of molecules of reactants will not always make the same amount of molecules of products. This is the same for every individual reaction.
Ex: N2 + 3H3 = 3NH2 (1 nitrogen molecule, 3 hydrogen molecules, (reactants) 2 Ammonia molecules (products)

Question 8

Moles and an example

Answer 8

Avogardo’s Number - 6.022 x 10^23 = 1 mole
The coefficients of a balanced chemical equation represent the number of moles in reactants and products
Ex: N2 + 3H2 = 2NH3 (1 mole of nitrogen, 3 moles of hydrogen, 2 moles of ammonia)

Question 9

Mass and an example

Answer 9

A balanced chemical equation obeys the law of the conversion of mass
Mass can neither be created or destroyed but simply transferred.
Ex: N2 + 3H2 = 2NH3
Both sides are 34.08 g/mol

Question 10

Volume and an example

Answer 10

One mole of any gas occupies a volume of 22.4 L
N2 + 3H2 = 2NH3
22.4L +3(22.4) = 2(22.4)
22.4+67.2 = 44.8 L
Volume is not conserved in this instance it takes, more to make less. Not the same on both sides

Question 11

In a chemical reaction what does an insufficient quantity do

Answer 11

An insufficient quantity of any of the reactants will limit the amount of products that forms

Question 12

Limiting reagent

Answer 12

The reactant that determines the amount of product that can be formed by a reaction

Question 13

Excess reagent

Answer 13

The reactant that is not completely used up in a reaction

Question 14

What is a limiter

Answer 14

The limiter is whichever in the smallest answer

Question 15

Theoretical yield

Answer 15

The maximum amount of product that could be formed from given amounts of reactants.

Question 16

Actual yield

Answer 16

The amount of product that actually forms when a reaction is carried out in the laboratory.

Question 17

Percent yield: How to find

Answer 17

The ratio of the actual yield to the theoretical yield expressed as a percent. (Actual/theoretical (100))

Question 18

Percent yield facts

Answer 18

1) Percent yield is a measure of the efficiency of a reaction carried out in a laboratory
2) Yields of greater than 100% are not possible
3) Actual yield is an experimental value, and can often be affected

Question 19

What can you do when you know the quantity of one substance in a reaction

Answer 19

You can calculate the quantity of any other substance consumed or created in the reaction

Question 20

Mass-to-mass calculations

Answer 20

1) convert the mass of the reactant or products to moles by using the molar mass ( 1mole what you have/grams of what you have)
2) Then use mole ratio to determine number of moles (coefficient and what you want/coefficient and what you have)
3) Convert back to grams by using the molar mass (Grams of what you want/1 mole of what you want)

Question 21

What two things are conserved in a balanced chemical equation?

Answer 21

Mass and charge

Question 22

What number is used to calculate mole ratios

Answer 22

Coefficients