C3 QUANTITATIVE CHEMISTRY
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law of conservation of mass?
no atoms are lost or made during a chemical reaction so the mass of the products equals the mass of the reactants
what is the relative formula mass? CaF2
Ca = 40 F = 19 Ca = 40 + (19 x2) = 78
the following reaction occurs in a test tube under a bunsen burner: 4MgO + CH4 -> 4Mg + 2H20 + CO2 the carbon dioxide and water escapes from the test tube explain why?
both gases
avogrado constant?
number of atoms, molecules , ions in a mole of a given substance. the value of the constant is 6.02 x 10 to the power of 23
formula that links mass , molecular mass , and moles together
mass = mr x moles
what is the mass of 20 moles of calcium carbonate CaCO3?
Mass = Mr x Moles Mr = 100 100 X 20 = 2000g
calculate the amount of carbon dioxide in moles in 0.32g of carbon dioxide. relative atomic masses = carbon = 12 , oxygen = 16
Moles = Mass/Mr 0.32/44 = 0.007
calculate the mass of nitrogen needed to form 6.8 tonnes of ammonia?
s1. work out the number of moles of ammonia (Mr of ammonia = 17) s2. 6800000/17 = 400000 moles of ammonia s3. use the balanced equation and number of moles of ammonia to work out the number of moles of nitrogen. s4. the ratio of nitrogen to ammonia is 1:2 s5. therefore the number of moles of nitrogen is 400000/2 = 200000 s6. work out the mass of nitrogen (mr of N2 is 28) s7. 200000 x 28 = 5600000g =5.6tonnes
limiting reactant?
the reactant that is all used up
how much oxygen will be given off from 40.8 g of hydrogen peroxide?
balanced equation - 2H202 -> 2H20 + O2 number of moles in 40.8g: 40.8/34 = 1.2 moles ratio in balanced equation of H2O2:O2 = 2:1 therefore the number of moles of o2 = 0.6moles mass of oxygen = 0.6 x 32 (Mr of o2) = 19.2
2 formulas that link concentration , mole/mass and volume together
concentration (g per dm cubed) = mass (g)/volume (dm cubed) concentration (mole per dm cubed) = nr of moles/volume (dm cubed)