Quantitative Chemistry Flashcards
Use your Periodic Table to find the relative atomic mass, Ar (or RAM), of carbon.
12 (not 6!)
Use your Periodic Table to find the relative atomic mass, Ar (or RAM), of bromine.
80
Use your periodic table to calculate the relative molecular mass, Mr (or RAM) for water, H2O
H + H + O = 1 + 1 + 16 = 18
Use your periodic table to calculate the relative molecular mass, Mr (or RAM) for calcium carbonate, CaCO3
Ca + C + O + O + O = 40 + 12 + 16 + 16 + 16 = 100
Calculate the percentage by mass of oxygen in water
Mass of O/Mr x 100 = 16/18 x 100 = 89%
Calculate the percentage by mass of hydrogen in water
Mass of H/Mr x 100 = 1+ 1/18 x 100 = 11%
What name is given to the quantity obtained by weighing out the Ar of any element or the Mr of any compound in grams?
1 mole
Why is the quantity of 1 mole important?
1 mole of any substance contains the same number of particles. This number is huge: 6.02 x 10exp23
What is the mass of 1 mole of argon atoms?
40g
What is the mass of 2 moles of nitrogen molecules, N2?
1 mole = 14 + 14 = 28g, so 2 moles = 28 x 2 = 56g
How much hydrogen chloride can be obtained from 100g of hydrogen?
H2 + Cl2 –> 2HCl
3650g
Calculate the mass of magnesium sulphate that would be obtained from 4g of magnesium.
Mg + H2SO4 –> MgSO4 + H2
20g
What is the yield?
The mass of product obtained in the reaction
What is the theoretical yield?
The theoretical yield is the maximum amount that can possibly be obtained in a reaction.
What is the actual yield?
The actual yield is the amount that is actually obtained.
Why is the actual yield usually less than the theoretical yield?
Some product might be lost or spilled, the reaction may be reversible, unwanted reactions might take place.
What is the percentage yield for a reaction where the theoretical yield of a product was 21g and only 3.8g was actually obtained?
3.8 / 21 x 100 = 18%
Titanium can be extracted from titanium chloride. The maximum theoretical mass of titanium that can be extracted from a sample is 72g. In the reaction, only 20 g of titanium was made. Calculate the percentage yield.
20 / 72 x 100 = 28%
Give the definition of molecular formula
The actual number of the atoms of each element present in the compound.
Give the definition of empirical formula
The simplest ratio of the atoms of each element present in the compound.
What is the empirical formula of ethane, C2H6?
CH3
What is the empirical formula of glucose, C6 H12 O6?
CH2O
A sample of calcium carbide contains 120g calcium and 72g of carbon. Calculate the empirical formula.
CaC2
14.2g of a sample of copper oxide contains 12.6g of copper. Calculate the empirical formula.
Cu2O
Balance this equation:
CH4 + O2 → CO2+ H2O
CH4 + 2O2 → CO2+ 2H2O
