Chemistry Topic 3- Quantitative Chemistry

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What is relative formula mass?
The relative atomic masses of all the atoms in the molecular formula added together.
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What is the formula for percentage mass of an element in a compound?
RAM x (number of atoms of that element) / (RFM of the compound) x 100
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What is the Avogadro number?
6.02 x 10 ^23
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How are moles are RFM related?
One mole of an atom/molecule will have a mass (in grams) equal to the RFM of that substance.
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What is the formula for number of moles?
Mass in grams / RFM
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What is meant by conservation of mass?
In a chemical reaction, no atoms are destroyed and no atoms are created- so there is no mass lost or gained.
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Why might mass change before and after an experiment?
Either one of the products is a gas (decrease in mass) or one of the reactants is a gas (increase in gas)
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How do you balance equations using reacting masses (empirical formula)?
Mass/RAM= Moles, then divide by smallest to give ratio
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When does a reaction stop?
When one of the reactants is used up- the limiting reactant.
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What is the relationship between the amount of product formed and the amount of limiting reactant?
The amount of product formed is directly proportional to the amount of limiting reactant.
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What is the volume of one mole of any gas at room temperature and pressure (20 degrees and 1 atm)?
24cm^3
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What Is the formula for volume of gas?
mass of gas / RFM of gas x 24
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What is the formula for concentration?
mass OR number of moles of solute / volume of solvent
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How do you convert cm^3 to dm^3?
/1000
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How do you convert mol/dm^3 to g/dm^3
mass = moles x RFM
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What is atom economy and how do you calculate it?
It tells you how much of the mass of the reactants is wasted when manufacturing a chemical and how much ends up as useful products. RFM of desired products/RFM of all reactants x 100
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What is the yield?
The mass of product. In practice you never get 100% of the yield, so the amount of product will be less than calculated.
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What is the formula for percentage yield?
Mass of product actually made / maximum theoretical mass of product x 100
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What are the three common problems that cause low yield?
Not all reactants react to make the product, there might be side reactions (e.g. with gases in the air), you lose some product when you separate it from the reaction mixture (e.g. by filtering a liquid, or transferring to container).
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Card 2

Front

What is the formula for percentage mass of an element in a compound?

Back

RAM x (number of atoms of that element) / (RFM of the compound) x 100

Card 3

Front

What is the Avogadro number?

Back

Preview of the front of card 3

Card 4

Front

How are moles are RFM related?

Back

Preview of the front of card 4

Card 5

Front

What is the formula for number of moles?

Back

Preview of the front of card 5
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