Calculating limiting reactants

Question 1

Calculating limiting reactants

Answer 1

1. Balance the symbol equation
2. Calculate moles of each substance
3. Find molar ratio
4. Calculate number of moles used in reaction
5. State limiting reactant

Question 2

Calculate molecular formula from empirical formula

Answer 2

1. Find Ar of each element
2. Calculate Mr of empirical formula
3. Divide molecular formula Mr by empirical formula Mr
4. Times formula by value to get molecular formula

Question 3

Calculate theoretical yield

Answer 3

1. Underline substances in equation questioned
2. Calculate Mr of substances
3. Find mass made by 1g of reactant
4. Times mass by mass of reactant in question

Question 4

Calculating the number of particles

Answer 4

Number of particles = moles x avogadros consant

6.02 x 10²³

Question 5

Calculate molar gas volume

Answer 5

Molar volume = 24dm³

Volume = moles x molar volume

Question 6

Calculate empirical formula from mass

Answer 6

1. Find Ar of each element
2. Divide mass of each element by its Ar
3. Divide the answers by smallest value to find ratio
4. Write out empirical formula

Question 7

Calculate relative formula mass from relative mass and abundance of isotopes

Answer 7

Total mass of atoms ÷ number of atoms (100)

Question 8

Calculating mass of reactants or products

Answer 8

1. Underline substance of given mass and substance whose mass you are finding
2. Find Mr for each substance
3. Workout molar ratio
4. Divide Mr of unknown mass by Mr of known mass
5. Times by known mass

Question 9

Calculate concentration from moles

Answer 9

Conc = moles÷volume
Volume in dm³
Cm³÷1000

Question 10

Calculating converting conc in gdm‐³ to mole dm‐³

Answer 10

Conc mol dm‐³ = conc in gdm‐3 ÷ Mr of solute

Question 11

Calculate conc from mass

Answer 11

Conc = mass÷volume

Question 12

Calculating moles

Answer 12

Mass = Mr x moles

Question 13

(Paper 2) calculating bond energies

Answer 13

1. Draw structural formula
2. Calculate energy in to break bonds
3. Calculate energy out during bond formation
4. Calculate energy difference —exo +edno

Question 14

Titration calculations

Answer 14

1. Write out balanced equation
2. Underline reactants needed
3. Deduce molar ratio
4. Convert volume to dm-³
5. Draw table and substitute values
6. Find moles of known conc 7. Use molar ratio to find moles of unknown substance
7. Substitute values into table
8. Find conc of unknown substance

Question 15

Deduce balanced equations from mass

Answer 15

1. Find number of moles of substances with known masses
2. ÷ by smallest value
3. Write formulae and known balanced number
4. Finish balancing equations

Question 16

Calculating atom economy

Answer 16

Mr of desired product÷sum of Mr of all reactants (x 100)

Question 16

Calculating atom economy

Question 16

Calculating atom economy

Question 17

Calculating Rf

Answer 17

Distance moved by solute÷distance moved by solvent

Question 18

Calculate % yield

Answer 18

Actual yield÷theoretical yield