C4, Stoichiometry

Question 1

Define Relative atomic mass Aᵣ

Answer 1

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

Question 2

Define molecular formula (of a compound)

Answer 2

the number and type of different atoms in one molecule

Question 3

Define relative molecular mass Mᵣ

Answer 3

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

Question 4

Relative formula mass Mᵣ

Answer 4

is used for ionic compounds

Question 5

Define mole

Answer 5

the unit of amount of substance. 1 mole contains 6.02 x 10²³ particles. This number is called the Avogadro constant

Question 6

molar mass

Answer 6

-mass of 1 mole of a substance
-relative formula mass in grams

Question 7

formula of
mass,
relative formula mass,
and number of moles

Answer 7

m = n x Mᵣ

Question 8

steps to calculate reactive masses [4]

Answer 8

1. identify 2 substances
2. calculate the relative formula mass for the two substances
3. calculate the number of moles
4. calculate the missing mass

Question 9

Describe what a limiting factor is

Answer 9

the reactant that is used up first

Question 10

Describe what an excess reactant is

Answer 10

the remaining reactant after the other reactant is used up

Question 11

define empirical formula

Answer 11

a formula giving the proportions of the elements present in a compound

Question 12

(aq)

Answer 12

aqueous solutions
substances dissolved in solvent

Question 13

formula of
Volume
molar gas volume
number of moles

Answer 13

n = V/Vₘ

Question 14

define Molar gas volume [2]

Answer 14

-volume occupied by one mole of a chemical element or a chemical compound
-taken as 24dm³ at room temperature and pressure

Question 15

Conversion between cm³ and dm³

Answer 15

1000cm³ = 1dm³
/1000 or x1000

Question 16

how do you convert from grams to mol?

Answer 16

divide by Mᵣ

Question 17

how do you convert from g/cm³ to g/dm³

Answer 17

multiply the ratio like a fraction x1000