chapter 1 formulae

Question 1

Avogadro constant

Answer 1

6.02x1023mol-1

Question 2

number of moles

Answer 2

mass/molar mass (m/MR)

Question 3

empirical formulae

Answer 3

1. Divide the amount of each element present by its molar mass, this will give you the molar ratio
2. Divide the answer for each element by the smallest number, the ensures your ratio is in the format 1: x
3. If necessary, multiply the answer by a suitable value to make sure the ratio is in whole numbers only, for example to have a whole number ration you would need to multiply the ration 1:1.5 by 2 to make it 2:3

Question 4

molecular formulae

Answer 4

1. The molecular formula is usually the same as the empirical formula or a whole number multiple of it

Question 5

gas volumes

Answer 5

n=v(dm3)/24.0 or n=v(cm3)/24000

Question 6

ideal gas equation

Answer 6

pV=nRT
p= pressure 1atm=101325 pa
v= volume 1m3=1000dm3
n= number of moles
R= gas constant with a value of 8.314 mol-1k-1 (don't need to remember)
T= temperature 0c=273 K

Question 7

concentration

Answer 7

n=cxv(dm3) or n=cxv(cm3)/1000

Question 8

percentage yield

Answer 8

actual amount in mol of product/ theoretical amount in mol of product x 100

Question 9

atom economy

Answer 9

molecular mass of desired product/ sum of molecular masses of all products x 100

Question 10

sulphuric acid

Answer 10

H2SO4

Question 11

hydrochloric acid

Answer 11

HCL

Question 12

nitric acid

Answer 12

HNO3

Question 13

salts from carbonates

Answer 13

acid + carbonate = salt + water + carbon dioxide

Question 14

salts from metal oxides

Answer 14

acid+ metal oxide= salt +water

Question 15

salt from alkalis

Answer 15

acid + alkalis = salt+ water

Question 16

salt from metals

Answer 16

acid +metal = salt +hydrogen

Question 17

acid base titrations

Answer 17

n= cxv

Question 18

dot formula

Answer 18

find water molecules