Molecular formulae

Question 1

the molecular formula of a compound shows

Answer 1

the actual numbers of atoms of each element in the compound

Question 2

to determine the molecular formula of a compound you need

Answer 2

the empirical formula and the relative molecular mass

Question 3

to determine the molecular formula mass of a compound, you compare the

Answer 3

relative molecular mass of the empirical formula with the the relative molecular mass of the actual compound to find the difference between the two, and use this (eg. x2) to work out the molecular formula

Question 4

moles =

Answer 4

mass / Mr

Question 5

the abbreviation of moles is

Answer 5

mol

Question 6

one disadvantage of using relative molecular mass is

Answer 6

that it can only be used for compounds containing covalent bonds (molecules)

Question 7

relative molecular mass can only be used for

Answer 7

molecules

Question 8

relative formula mass can be used

Answer 8

for both molecular and ionic compounds

Question 9

molar mass is

Answer 9

the mass per mole of a substance (molar or ionic), it has the symbol M and the units g mol-1

Question 10

calculating moles using molar mass =

Answer 10

amount in mol= mass of substance in g / molar mass in g mol-1

Question 11

n=

Answer 11

n=m/M

Question 12

the ideal gas equation is

Answer 12

pv=nRT

Question 13

the ideal gas equation is used for

Answer 13

gases and volatile liquids above their boiling temperatures

Question 14

the SI units for the ideal gas equation are:

Answer 14

p= pressure in pascals (Pa)
V= volume in cubic metres (m3)
T= temperature in kelvin (K)
n= amount of substance in moles (mol) 
R= the gas constant, 8.31 J mol-1 K-1

Question 15

kPa - Pa conversion=

Answer 15

x 1000

Question 16

cm3 - m3 conversion=

Answer 16

divide by 1,000,000

Question 17

dm3 - m3 conversion=

Answer 17

divide by 1000

Question 18

degrees C - degrees K conversion=

Answer 18

+ 273