How many particles in a mole?
What are moles a quantity of?
Amount of substance
Number of particles =
number of moles x 6.02×10(23)
What is molar mass?
Molar mass is the gram equivelent of the relitive atomic mass on the periodic table, the mass of one mole of a substance
number of moles x molar mass
number of moles / volume of solution
one litre =
1dm3 = 1000ml = 1000cm3
0 Kelvin =
-273 degrees C
Equal volumes of gas contain equal moles of gas
1.0 moles of gas occupies
22.4dm3 @ standard conitions
percent yield =
experimental yield / Theoretical Yield x 100%
1.7 g of NaNO3 (Mr = 85) is dissolved in water to prepare 0.20 dm3 of solution. What is the concentration of the resulting solution in mol dm-3?
The relative molecular mass of a gas is 56 and its empirical formula is CH2. What is the molecular formula of the gas?
What mass, in g, of hydrogen is formed when 3 mol of aluminium react with excess hydrochloric acid according to the following equation?
2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g)
What is the total number of hydrogen atoms in 1.0 mol of benzamide, C6H5CONH2?
4.2 × 1024
A fixed mass of gas has a certain volume at a temperature of 50 °C. What temperature is required to double its volume while keeping the pressure constant?
Chloroethene, C2H3Cl, reacts with oxygen according to the equation below.
2C2H3Cl(g) + 5O2(g) →
4CO2(g) + 2H2O(g) + 2HCl(g)
What is the amount, in mol, of H2O produced when 10.0 mol of C2H3Cl and 10.0 mol of O2 are mixed together, and the above reaction goes to completion?
Equal masses of the metals Na, Mg, Ca and Ag are added to separate samples of excess HCl(aq).
Which metal produces the greatest total volume of H2(g)?
5 dm3 of carbon monoxide, CO(g), and 2 dm3 of oxygen, O2(g), at the same temperature and pressure are mixed together. Assuming complete reaction according to the equation given, what is the maximum volume of carbon dioxide, CO2(g), in dm3, that can be formed?
2CO(g) + O2(g) → 2CO2
Which of the following has the greatest mass?
A. 6 x 1025 atoms of helium gas
B. 10 moles of oxygen molecules
C. 1.2 x 1024 atoms of copper
D. 1 mole of gold atoms
A. 6 x 1025 atoms of helium gas
Barium peroxide, BaO2, decomposes when heated to give BaO and O2.
2BaO2 –> 2BaO + O2
If 0.500 mol of BaO2 is decomposed, the number of moles of O2 formed is
Which of the following is an empirical formula?
How many grams of AgCl would be precipitated if an excess of AgNO3 solution were added to 55.0 cm3 of 0.200 M KCl solution?
AgNO3(aq) + KCl(aq) –> KNO3(aq) + AgCl(s)
0.2 x (55/1000) = 0.011 mol of KCl
Which also = 0.011 mol of AgNO3
Mass = mol x Mr = 0.011 x 143 = 1.573g
A Household cleaners contains ammonia. 25.37g of this cleaner is dissolved in water and made up to 250 cm3. A 25.0 cm3 portion of this solution requires 37.3 cm3 of 0.360 mol/dm3 sulphuric acid for neutralisation.
What is the percentage by mass of ammonia in the cleaner ?
2NH3(aq) + H2SO4(aq) –> (NH4)2SO4 (aq)
Moles H2SO4 = 0.360 x (37.3/1000) = 1.332 x 10 -2 mol H2SO4 in 25cm3
Moles of NH3 = 2 x 1.332 x 10 -2 = 2.664 x 10 -2 mol in 25cm3
In 250 cm3 = 2.664 x 10 – 1 mol NH3
Mass NH3 = 0.2664 x 17 = 4.57g
% mass = (4.57 / 25.37) x 100 = 18.0%
Hydrogen sulphide burns in oxygen according to the following equation
2H2S(g) + 3O2(g) –> 2H2O(g) + 2SO2(g)
If 4dm3 of H2S are burned in 10 dm3 of oxygen, what is the final volume of the mixture? (assume that all volumes are measured at the same temperature and pressure).
4dm3 H2S needs 6dm3 of O2
Therefore O2 is in excess.
H2S = limiting reagent
All H2S react to produce 4dm3 H2O and 4dm3 SO2
8 dm3 of products plus 10 -6 = 4 dm3 of O2 left over
So 12 dm3 of final mixture
An organic compound has the composition by mass of 83.5% carbon, 6.4% hydrogen and 10.1% oxygen. The molar mass of the compound is 158 g mol-1. Determine the molecular formula of the compound.
Carbon 83.5 / 12 = 6.96
Hydrogen 6.4 / 1 = 6.4
Oxygen 10.1 / 16 = 0.63
There froe divide all answers by 0.63
Carbon = 6.96 / 0.63 = 11
Hydrogen = 6.4 / 0.63 = 10
Oxygen = 0.63 / 0.63 = 1
A 25.0 g sample of an oxide of copper, when heated in a stream of hydrogen, forms 3.15 g of water. Find the percentage of copper by mass in the compound.
Hint: The Hydrogen removes the copper from the water.
CuO + H2 –> Cu + H2O
Moles H2O = 3.15 / 18 = 0.175 mol
This also = 0.175 mol O in compound
Mass of O = 0.175 x 16 = 2.8g
Therefore, mass of Cu in compound = 25.0 = 2.8 = 22.2g
% by mass = (22.8 / 25) x 100 = 88.8%