1.2 Calculations Flashcards
How many particles does one mole contain?
6.022 x10^23
How to calculate the number of particles in a substance.
Number of particles =
Number of moles x Avagadro’s constant
How to calculate the number of moles with a given mass.
Number of moles =
Mass of substance / Mr
How to calculate the number of moles with a given volume/concentration of solution.
Number of moles =
Concentration (mol dm-3) x Volume (dm3)
What is the ideal gas equation?
pV = nRT
Where: p = pressure (Pa) V = volume (m3) n = number of moles R = Gas constant - 8.31 JK-1mol-1 T = temperature (K)
How many meters3 are in 1 cm3 and 1 dm3?
1cm3 = 1 x10-6 m3 1dm3 = 1 x10-3 m3
Balance this equation:
C2H6 + O2 -> CO2 + H2O
(see page 16 in the revision guide)
Write the ionic equation for the reaction of nitric acid with sodium hydroxide.
HNO3 + NaOH -> NaNO3 + H2O
(see page 16 in the revision guide)
What do these state symbols mean?
s
l
g
aq
s = solid l = liquid g = gas aq = aqueous
Calculate the mass of iron oxide produced if 27.9g of iron is burnt in air.
4Fe + 3O2 -> 2Fe2O3
39.9g
see page 17 in the revision guide
What volume of gas, in dm3, is produced when 15.0g of sodium reacts with excess water at a temperature of 25.0 degrees C and a pressure of 100 kPa? Gas constant is 8.31 J K-1 mol-1
2Na (s) + 2H2O (l) -> 2NaOH (aq) + H2 (g)
8.07dm3
see page 17 in the revision guide
Explain how you would make 250cm3 of a 2.00 mol dm-3 solution of sodium hydroxide.
(see page 18 in the revision guide)
How do you carry out a titration?
(see page 18 and 19 in the revision guide)
What colour does methyl orange change from and to in the presence of an acid and an alkali?
acid - red
alkali - yellow
What colour does phenolphthalein change from and to in the presence of an acid and an alkali?
acid - colourless
alkali - pink
In a titration experiment, 25.0 cm3 of 0.500 mol dm-3 HCl neautralised 35.0 cm3 of NaOH solution. Calculate a concentration of the sodium hydroxide solution is mol dm-3.
(see page 19 in the revision guide)
20.4cm3 of a 0.500 mol dm-3 solution of sodium carbonate reacts with 1.50 mol dm-3 nitric acid. Calculate the volume of nitric acid required to neutralise the sodium carbonate.
(see page 20 in the revision guide)
What is the empirical formula?
The empirical formula gives just the simplest whole number ratio of atoms of each element in a compound.
What is the molecular formula?
The molecular formula gives the actual numbers of each atoms of each element in a compound.
A molecule with Mr = 166.0 has the empirical formula C4H3O2. Find its molecular formula.
(see page 21 in the revision guide)
A compound is found to have percentage composition of 56.5% potassium, 8.70% carbon and 34.8% oxygen by mass. Find its empirical formula.
(see page 21 in the revision guide)
When a hydrocarbon is burnt in excess oxygen, 4.40g of carbon dioxide and 1.80g of water are made. What is the empirical formula of the hydrocarbon?
(see page 21 in the revision guide)
How to calculate percentage yield?
Percentage Yield =
Actual Yield / Theoretical Yield x 100
(see page 22 in the revision guide for an example)
0.475g of CH3Br reacts with excess NaOH in the following reaction:
CH3Br + NaOH -> CH3OH + NaBr
0.153g of CH3OH is produced. What is the percentage yield?
(see bottom of page 22 in the revision guide)