Physical 2: Amount of Substance

Question 1

What is relative atomic mass?

Answer 1

The average mass of an element relative to 1/12th of the mass of one atom of carbon 12

Question 2

What is relative molecular mass?

Answer 2

The average mass of a molecule relative to 1/12th of the mass of one atom of carbon 12

Question 3

What is the Avogadro constant and what can it be used for?

Answer 3

6.022x10^23
Can be used to calculate the mass of an atom
1 mole = 6.022x10^23 atoms

Question 4

How do you convert 1dm to cm?

Answer 4

Multiply by 10
(1dm = 10cm)

Question 5

How do you convert 1dm3 to cm3?

Answer 5

Multiply by 1000
(1dm3 = 1000cm3)

Question 6

What is the ideal gas equation?

Answer 6

PV = nRT
P = pressure (Pa)
V = volume (m^3)
n = number of moles
R = gas constant
T = temperature (K)

Question 7

How do you convert from degrees Celsius to Kelvin?

Answer 7

+ 273

Question 8

How do you convert cm^3 to m^3?

Answer 8

x10^-6

Question 9

What is an empirical formula?

Answer 9

The simplest whole number ratio of the atoms present in a compound

Question 10

How do you calculate empirical formula?

Answer 10

1) Find the masses of each element present in a compound
2) Work out the number of moles of atoms of each element
3) Convert the number of moles of each element to a whole number ratio

Question 11

How do you find molecular formula from empirical formula?

Answer 11

Divide the molecular mass of the compound by the molecular mass of the empirical formula to find a scale factor
Multiply the empirical formula by this scale factor

Question 12

How do you calculate atom economy?

Answer 12

% Atom economy = (mass of desired product / total mass of reactants) x 100

Question 13

How do you calculate percentage yield?

Answer 13

Percentage yield = moles of desired product/moles of theoretical product x 100