Quantitative Chemistry Equations (Numerical)

Question 1

What equation links the number of moles, mass and Mr?

Answer 1

Mass = no. of moles x Mr

Question 2

What equation links the number of particles, moles and avogadros number?

Answer 2

Number of particles = moles x avogadros number

Question 3

How do you find out the percentage of a substance in a compound?

Answer 3

(Mr of Substance) / (Mr of the whole compound) x 100

Question 4

What is the uncertainty of a reading?

Answer 4

Plus or minus half of the smallest division on the equipment

Question 5

How do we calculate the percentage uncertainty/ error?

Answer 5

(Overall uncertainty/ Value) x 100

Question 6

How do we find out the overall apparatus error?

Answer 6

The sum of the individual errors

Question 7

How do we calculate the percentage yield?

Answer 7

(Actual yield of product/ theoretical yield of product) x 100

Question 8

How do we calculate the percentage atom economy?

Answer 8

(Total Mr of desired product/ total Mr of reactants/ products) x 100

Question 9

What is the ideal gas equation?

Answer 9

PV=nRT

Question 10

What is the value of R (the ideal gas constant)?

Answer 10

8.31 J k-1 mol-1

Question 11

How do you convert degrees celcius to kelvin?

Answer 11

Add 273

Question 12

How do you convery MPa to Pa?

Answer 12

times by 1000000

Question 13

How many Pa is 1atm?

Answer 13

101000 Pascals

Question 14

How many litres is 1000cm3?

Answer 14

1 litre

Question 15

What is the equation for concentration with volume in dm3?

Answer 15

concentration = moles / volume (dm3)

Question 16

What is the equation for concentration with volume in cm3?

Answer 16

concentrayion = (moles x 1000) / volume (cm3)
n=cv/1000

Question 17

What is the maximum error for a burette in a titration?

Answer 17

plus or minus 0.15cm3 (2 readings and an end point error)
= (0.15/ average titre) x 100

Question 18

What is the maximum error for a pipette in a titration?

Answer 18

plus or minus 0.05cm3
= (0.05/25) x100 = 0.2%