Chemical Calculations

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  • Created by: zoolouise
  • Created on: 24-04-16 19:23
What is Avogadro's Constant?
6.02x10^3
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What is the equation for the amount of a substance in moles?
amount in moles (n) = mass (m) / molar mass (M)
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What is the definition of Molar mass?
Molar mass is the mass of one mole of a substance
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What is the definition of Avagadro's constant?
The Avogadro constant is the number of atoms per mole.
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What is the definition of stoichiometry?
Stoichiometry is the molar relationship between the amounts of reactants and products in a chemical reaction
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What is the definition of empircal formula?
Empirical formula is the simplest formula showing the simplest whole number ratio of the amount of elements present
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What is the definition of molecular formula?
Molecular formula shows the actual number of atoms of each element present in the molecule. It's a simple multiple of the empirical formula.
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How do you calculate the empirical formula?
1) Find amount in moles of each element (divide number given by molar mass) 2) Find ratio of number of atoms present (divide numbers by smallest value obtained from step 1) 3) Convert these numbers into whole numbers if not already
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How do you calculate the molecular formula?
1) Find the mass of the compound 2) Divide the molecular mass by the mass of the compound 3) Multiply existing empirical formula by value obtained from step 2
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What must the volume be measured under?
The same conditions of temperature and pressure.
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What is the gas molar volume?
At standard temperature and pressure (stp) 0 degrees celcius and 1atm, tone mole of any gas occupied 22.4dm^3
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What is the definition of The Molar volume?
The Molar volume, Vm, is the volume per mole of gas.
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What are the steps in calculations involving molar volume?
1) Change mass into moles 2) Work out how much gas is produced from the ratio of the compound 3) Change moles into volume of gas (multiply by 22.4)
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What is Boyle's law?
At a constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure. V ∞ 1/P or PV = constant
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What is Charle's law?
The volume of a fixed mass of a given gas, at constant pressure, is directly proportional to its temperature in kelvins. V ∞ T or V/T = constant
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What is Avogadro's principle?
Equal volume of different gases, measured at the same temperature and pressure, contain the same number of molecules. V ∞ n
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What is the ideal gas equation?
A combination of Boyle's law and Charle's law following from Avogadro's hypothesis. PV/T = nr or PV = nRT
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What must the Sl units be?
Pressure must be in PA (pascals). Volume must be in m^3. Temperature must be in K (Kelvins)
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What is the value of R?
R is the gas constant, it has the value of 8.314JK-1mol^-1
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What does the concentration of a solution measure?
The concentration of a solution measured how much of a dissolved substance is present per unit volume of a solution.
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What is a concentrated solution?
A solution with a large quantity of solute in a small quantity of solvent.
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What is a dilute soolution?
A solution with a small quantity of solute in a large quantity of solvent.
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What's the calculation to work out concentration?
Concentration = amount of moles of solute/volution of solution or c = n/V
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What's the steps in calculating a concentration?
1) Change mass into moles (divide by molar mass) 2) Change cm^3 into dm^3 (divide by 1000) 3) Divide the moles by the volume
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What are the steps in an acid-base titration calculation?
1) Find amount of moles of solution you know the concentration of. (e.g. acid) 2) Use balanced chemical equation to give ratio between acid and base 3) Calculate concentration in second solution (e.g. base) from known volume and amount of moles
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What is atom economy and percentage yield?
An indication of the efficiency of a reaction
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What happens the higher the atom economy?
The more efficient the process
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What is the equation for atom economy?
Atom economy = (mass of required product / total mass of reactions) x 100%
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What is the equation for percentage yield?
Percentage yield = (mass (or moles) of product obtained / maximum theoretic mass (or moles)) x 100%
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Card 2

Front

What is the equation for the amount of a substance in moles?

Back

amount in moles (n) = mass (m) / molar mass (M)

Card 3

Front

What is the definition of Molar mass?

Back

Preview of the front of card 3

Card 4

Front

What is the definition of Avagadro's constant?

Back

Preview of the front of card 4

Card 5

Front

What is the definition of stoichiometry?

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