# Quantitative Chemistry

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What is relative atomic mass?
Relative atomic mass is often abbreviated to Ar. For each element, it's Ar is the same as it's mass number.
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What is relative formula mass?
Relative formula mass is often abbreviated to Mr. It is simply all of the relative atomic masses in a compound added together
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What is percentage mass?
This works out the amount of an element (by percentage) that is in a compound.
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How do you work out percentage mass?
Percentage mass is the Ar x the number of atoms of that element (e.g. Ar of Oxygen = 8
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What is an empirical formula?
This gives you the simplest formula of a compound.
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How do you work out empirical formula?
List all of the elements in the compound and write their masses given to you in grams. Next, divide each mass by the Ar (mass number) of that element. Then divide these numbers by the smallest one that was previously produced to give you a ratio.
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How do you calculate masses in reactions?
First, write out the balanced equation. Next, write out the elements and the mass in grams you are given for one of them. To work out the number of moles, divide the mass in grams by the atom's Mr.
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Continued..
To work out the moles of the other atom, divide the mole you have already worked out by that atom's ratio and times it by the ratio of the other atom. Finally, to get the other atom's mass, times it's mole by it's Mr.
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What is percentage yield?
Percentage yield compares actual and theoretical yield and they are always less than 100%. The yield of a reaction is the mass of product it produces.
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How to work out percentage yield?
Take the actual yield (in grams) and divide it by the theoretical yield (in grams) X 100.
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Why are yields always less than 100%?
Incomplete reactions mean that not all reactions are converted to products. Practical losses during preparation means that you lose a bit when chemicals are transferred. Unwanted reactions mean that the yield of the intended product goes down.
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## Other cards in this set

### Card 2

#### Front

What is relative formula mass?

#### Back

Relative formula mass is often abbreviated to Mr. It is simply all of the relative atomic masses in a compound added together

### Card 3

#### Front

What is percentage mass?

### Card 4

#### Front

How do you work out percentage mass?

### Card 5

#### Front

What is an empirical formula?