Unit 4 CHEM:S Stoichiometry

Question 1

Relative atomic mass Ar

Answer 1

The average mass of the isotopes in an element compared to 1/12th of the mass of an atom of C

Question 2

Molecular formula

Answer 2

A compound is defined as the number and type of diffusion atoms in one molecule

Question 3

Relative molecular mass

Answer 3

M is the sum of the relative atomic masses.Relative formula mass, Mᵣ, is used for ionic compounds.

Question 4

Relative formula mass

Answer 4

Mᵣ is used for ionic compounds

Question 5

Mol

Answer 5

Symbol mol is the unit of substance. 1 mole contains 6.02x10²³ particles, e.g. atoms, ions, and molecules. his number is called the Avogadro constant

Question 6

The steps to calculate reactant masses

Answer 6

CaCO3–>(1)CaO+ (2)CO2
(1) Identify 2 substances
(2) 1 N 23.4/100 2 N 0.234 mol
1 M 23.4g 2 M 0.234x44=10.3g
1 Mr 100 2 Mr 44
(3) Calculate n of moles+consider ratios(1=1)
(4) Calculate missing mass NxMr=M

Question 7

Limiting reactant

Answer 7

Is the thing that is used up first

Question 8

Excess reactants

Answer 8

To make sure the limiting reactant is fully used up.

Question 9

molar mass

Answer 9

the mass in grams of one mole of the compound

Question 10

molar gas volume

Answer 10

(n=V/Vm) The molar volume is the volume occupied by one mole of any gas, at room temperature and pressure. The molar volume is equal to 24 dm 3 (24,000 cm 3).

Question 11

concentration from g-mol

Answer 11

n=M/Mr