Chapter 3: Stoichiometry

Question 1

Mass spectrometer

Answer 1

An instrument used to determine the relative masses of atoms by the deflection of their ions on a magnetic field

Question 2

Mass of carbon-12

Answer 2

12 atomic mass units (standard for atomic mass)

Question 3

Mole

Answer 3

The number equal to the number of carbon atoms in exactly 12 grams of carbon-12

Question 4

Avogadro’s number

Answer 4

6.022 x 10^23

Question 5

One mole of anything is…

Answer 5

6.022 x 10^23 units of that substance

Question 6

Molar mass

Answer 6

The mass in grams of 1 mole of a compound

Question 7

Mass percent

Answer 7

The percent by mass of a given element in a compound

Question 8

Formula for mass percent

Answer 8

Total element mass/molar mass

Question 9

Empirical formula

Answer 9

The simplest whole-number ratio of atoms in a compound

Question 10

Molecular formula

Answer 10

The exact formula of a molecule, giving the types of atoms and the number of each type (multiple of the empirical formula)

Question 11

Process for determining the empirical formula of a compound

Answer 11

1. Convert the percentages of constituent elements to grams by assuming you have 100 grams of the compound (Skip if given the masses of the elements)
2. Convert the grams to moles
3. Divide each by the smallest number of moles
4. If any of the ratios is not a whole number, multiply all the ratios by a factor to make it a whole number
5. Use the ratios as the subscripts in the empirical formula

Question 12

Process for determining the molecular formula of a compound

Answer 12

1. Determine the empirical formula
2. Determine the molar mass of the empirical formula
3. Divide the given molar mass of the compound by the molar mass of the empirical formula

Question 13

Chemical equation

Answer 13

A representation of a chemical reaction showing the relative numbers of reactant and product molecules

Question 14

Reactant

Answer 14

A starting substance in a chemical reaction. It appears to the left of the arrow in a chemical equation.

Question 15

Product

Answer 15

A substance resulting from a chemical reaction. It is shown to the right of the arrow in a chemical equation.

Question 16

Balancing a chemical equation

Answer 16

Obeying the following rule:

All atoms present in the reactants must be accounted for among the products.

Question 17

Coefficient

Answer 17

Indicates the relative numbers of reactants and products in a reaction in the balanced equation

Question 18

Mole ratio

Answer 18

The ratio of moles of one substance to moles of another substance in a balanced chemical equation

Question 19

Limiting reactant

Answer 19

The reactant that runs out first and thus limits the amounts of products that can form

Question 20

Theoretical yield

Answer 20

The amount of a product formed when the limiting reactant is completely consumed

Question 21

Percent yield

Answer 21

The actual yield of products given as a percentage of the theoretical yield [(actual yield/theoretical yield)x100]

Question 22

Stoichiometry

Answer 22

Study of quantities of materials consumed and produced chemical reactions