Chem Math

Question 1

Mole

Answer 1

A unit of amount

Question 2

Gram formula mass (GFM)

Answer 2

The mass of one mole of a compound in grams

Question 3

How do you determine GFM?

Answer 3

Multiple the given mass for each element on the reference table by the number of those elements present, then add the products together

Question 4

How do you determine the percent mass composition of elements in a compound?

Answer 4

Total mass of element (basically GFM of one certain element)/total mass of compound (GFM of compound)

Question 5

Hydrate

Answer 5

A compound or crystal that contains H2O
CuSO4 . 5H2O (the dot is the symbol of a hydrate)

Question 6

Anhydrate

Answer 6

A compound or crystal that does not contain H2O

Question 7

How do you determine the percent mass of water in the hydrate?

Answer 7

GFM of just water/GFM of hydrate (don’t include the water in this calculation) x 100

Question 8

A sample of hydrate weighs 96.0 grams. After heating to remove all water, the anhydrate weighs 46.0 grams. What was the mass percent of water?

Answer 8

96.0 - 46.0 = 50.0 grams of water in the hydrate

50.0 grams/96.0 grams x 100 = 52.1%

Question 9

Molecular formula

Answer 9

Shows how many atoms of each element in the compound

Question 10

Empirical formula

Answer 10

Lowest whole number ratio of atoms in a compound

Question 11

How do you determine an empirical formula from prevent composition data?

Answer 11

1) Write the percents as grams
2) Divide the grams of each individual element by the GFM of each element
3) All answers are now in terms of moles
4) Divide all the moles by the smallest quotient identifies from the above steps
5) That should give you the whole number that you need to affiliate with each element

Question 12

How do you find the molecular formula of a substance given its molecular mass?

Answer 12

1) Use the molecular formula to find the empirical formula
2) Divide the molecular mass of the entire substance by the GFM of the entire substance
3) Multiply the quotient by each part of the empirical formula

Question 13

1 mol =

Answer 13

• 6.02 x 10^23 molecules
• 12 x 10^23 atoms (for HONClBrIF)
• Mass from periodic table
• 22.4 L of a gas at STP

Question 14

STP

Answer 14

Standard temperature and pressure

Question 15

Stoichiometry

Answer 15

Using balanced chemical equations to make quantitative relationships between reactants and products

Question 16

Mole ratio

Answer 16

Derived from the coefficients in a balanced chemical equation

Question 17

Conservation of mass

Answer 17

The mass of the reactants must equal the mass of the products

Question 18

Density

Answer 18

Mass/volume

Question 19

As temperature decreases,

Answer 19

Volume decreases and density increases

Question 20

As temperature increases,

Answer 20

Volume increases and density decreases