C4 : Quantitative Chemistry

Question 1

Explain the meaning of a mole (2)

Answer 1

• One mol of a substance is the amount fo substance that contains Avogadro’s number (6.02 x 10^23 particles)
• one mole of any substance contains the same no. units as one mole of any other substance .

Question 2

describe the link between the mole and the relative atomic mass of the element. (3)

Answer 2

• the value of the relative atomic mass of any element
• is EQUAL to the mass of one mole of that substance
• in grams.

Question 3

Formula for calculating no. moles?

Answer 3

n = m/M

Question 4

formula for atom economy?

Answer 4

mass (Mr) of desired PRODUCT / mass (Mr) of all REACTANTS x 100

Question 5

formula of yield ?

Answer 5

made/expected x100

Question 6

2 reasons why it is beneficial to get a high % atom economy ?

Answer 6

• sustainable development
• economic reasons
• waste products may be pollutants/harmful

Question 7

formula for concentration fo a solution?

Answer 7

conc (mol/dm^3) = moles/volume (dm^3)

Question 8

formula for gas volumes ?

Answer 8

no. moles of a gas = volume (dm^3) / 24dm^3

Question 9

Why does increasing the concentration have an effect on the rate of reaction? (3)

Answer 9

• a high concentration has MORE PARTICLES PER UNIT VOLUME
• bc they are closer together
• therefore more collisions

Question 10

what do titrations measure?

Answer 10

find out exactly the VOL OF ACID needed to neutralise a measured VOL OF ALKALINE

Question 11

titration METHOD?

Answer 11

1) USE PIPETTE AND PIPETTE FILLER to add VOL OF ALKALINE to conical flask - ADD INDICATOR TOO
2) use FUNNEL to add ACID INTO BURETTE of KNOWN CONC - record initial volume of acid in burette
3) Add acid into ALKALINE slowly and give regular SWIRLS - if near end point add slower
4) indicator changes colour if NEUTRALISED
5) Record FINAL VOL OF ACID IN BURETTE and use it along with INITIAL READING to calculate vol of acid to neutralise ALKALINE
6) REPEAT - RECORD MEAN