Chemistry C3 (Quantitative Chemistry)

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What does the law of conservation of mass state?
No atoms are lost or made during a chemical reaction so the mass of the products is equal to the mass of the reactants
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What is the relative formula mass of a compound?
It is the sum of the relative atomic masses of the atoms in the numbers shown in the formula
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Why do some reactions appear to have a change in mass?
Because the reactant or product is a gas and its mass hasn't been taken into accounted, or for example co2 escapes leaving a metal oxide as the only product
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What are chemical amounts measured in?
Moles
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What is the symbol for the unit mole?
mol
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What is the mass of one mole of a substance in grams numericallly equal to?
Its relative formula mass
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What does one mole of any substance contain?
The same number of stated particles,atoms, molecules or ions
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What is the number of atoms, molecules or ions in one mole of a given substance called?
Avogadro Constant
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What is the value of Avogadro Constant?
6.02 x 10^23 per mole
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What does the big number in front of chemical compounds/elements represent
The number of moles
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Why, jn a reaction invlolving 2 reactants, it is common to use an excess of one of the reactants?
To ensure that all the other reactant is used
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What is the reactant that is completely used up called and why?
The limiting reactant because it limits the amount of products
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What is the equation linking , moles, relative formula mass and mass?
moles= mass/relative formula mass
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What are 2 units of measurement of cocentration?
g/dm^3 and mol/dm^3
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How do you work out the concentration of a given solution if you know the amount(in moles or grams) and volume
concentration= amount(mol or g) / volume
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What units of measurement is volume?
dm^3
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How would you convert cm^3 to dm^3 to get the right unit for volume?
divide by 1000
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Why is it not always possible to obtain the calculated amount of a product?
May not go to completion as it is reversible, some of prodcut may be lost when separated form reaction mixture, some of reactants may react in ways different to expected reaction
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What is the amount of a product obtained known as?
The yield
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How do you work out the percentage yield ?
Mass of product actually made/Maximum theoretical mass of product x 100 (to make it a %)
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What is the atom economy?
Thge meausre of the amount of starting materials that end up as useful products
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How do you calculate the percentage atom economy?
Relative formula mass of desired product/Sum of relative formula masses of all reactants x 100 (to make it a %)
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Under the same conditions of temperature and pressure, what do equal amounts of moles occupy?
The same volume
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What does the volume of one mole of any gas at room temperature and pressure (20 degrees and 1 atmosphere pressure) equal?
24dm^3
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How do you work out the volume of a gas at rtp? (room temperature and pressure)
volume of gas at rtp = number of moles x 24(dm^3)
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Card 2

Front

What is the relative formula mass of a compound?

Back

It is the sum of the relative atomic masses of the atoms in the numbers shown in the formula

Card 3

Front

Why do some reactions appear to have a change in mass?

Back

Preview of the front of card 3

Card 4

Front

What are chemical amounts measured in?

Back

Preview of the front of card 4

Card 5

Front

What is the symbol for the unit mole?

Back

Preview of the front of card 5
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