Formulae, equations and amounts of substance

Question 1

Mole

Answer 1

amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon-12.

Question 2

Relative atomic mass

Answer 2

average mass of one atom compared to one twelfth of the mass of one atom of carbon-12

Question 3

Molar Mass

Answer 3

mass in grams of 1 mole of a substance and is given the unit of g mol-1

Question 4

Gas volume (dm3)

Answer 4

mole x 24

Question 5

cm3 –> dm3

Answer 5

divided by 1000

Question 6

cm3 –> m3

Answer 6

÷ 1000 000

Question 7

dm3 –> m3

Answer 7

÷1000

Question 8

Avogadro constant

Answer 8

number of particles equivalent to the relative atomic mass or molecular mass of a substance

Question 9

What is difference between relative molecular mass and relative formula mass

Answer 9

The mean mass of a molecule of a compound instead of mean mass of an atom of an element

Question 10

What is empirical formula

Answer 10

simplest whole number ratio of atoms of each element in a compound

Question 11

what is molecular formula

Answer 11

the actual number of atoms in the molecule . Determined by dividing the actual mr by the empirical mr

Question 12

Ideal gas equation

Answer 12

pV = nRT
p = pascals
V = m3
T = Kelvin
n = moles
R = 8.31 J K -1mol-1

Question 13

What is a titration

Answer 13

when a standard solution with a known concentration is reacted with solution of unknown concentration

Question 14

How to make a volumetric/ standard solution

Answer 14

weight sample bottle
transfer solid and reweigh
record difference in mass add distilled water and stir with glass rod till dissolved
transfer to volumetric flash with washings and mark up with 250cm3 of distilled water
shake flask

Question 15

How to carry out titration

Answer 15

measure standard solution into flash using volumetric pipette
add indicator
tap open portion by portion until colour change
multiple times carried out until concordant results obtained within 0.1cm3

Question 16

formula for concentration

Answer 16

number of moles of solute divided by volume of solution.
concentrated solution has high conc of solute

Question 17

how to work out mass when you have concentration and volume

Answer 17

conc x volume = n
n x molar mass = mass

Question 18

what is two types of errors

Answer 18

random and systematic

Question 19

what is a systematic error

Answer 19

poor designed procedure
if you forget to zero mass balance
don’t read burette at eye level

Question 20

formula for uncertainty

Answer 20

( instrument uncertainty / measurement ) x 100

Question 21

how can you reduce uncertainties

Answer 21

increase titre volume either increase volume and concentration in flask or decrease concentration in burette

Question 22

percentage yield

Answer 22

actual yield / theoretical yield x 100
maximum amount of product obtained

Question 23

why can there be a low percentage yield

Answer 23

loss during purification or separation
reaction isn’t completed
other reactions occur simultaneously

Question 24

Atom economy

Answer 24

efficiency, proportion of reactants converted into desired product

Mr of desired / Mr of total x 100