# Chemistry

• Created by: Mollie
• Created on: 02-03-14 13:01
What is the formula for percentage yield
percentage yield=actual yield/theoretical yield x 100
1 of 13
A scientist calculated that a reaction could be used to make 200g of sodium chloride. 175g was actually made. Work out the percetage yeild.
actual yield is 175g, theoretical yeild is 200. 175/200x100=87.5% (percentage yeild)
2 of 13
why do reactions rarely go to 100%?
The reaction may be reversible and unexpected products may be made.
3 of 13
What is chromatography?
Used to seperate additives used in food.
4 of 13
what is gas chromatography?
mixture is vaporised, carrier gas moves through column, compounds in mixture has attrations to partiicles, some tske longer to get through called retention time. compounds with shorter retention time leave column first.
5 of 13
What is mass spectrometry
used to find relative molecular mass of a compound
6 of 13
What is the formula for theoretical yeild
mass of reactant/(moles x Mr of reactant) x (moles x Mr of product)
7 of 13
2H2 + 02 ----> 2H20) How much water is produced from 8g of H2?
Mass of reactant is 8. 8/2x2g=4g. =8/4 -> x 2x18=36g. 8/4x36=72g. Every 8g of hydrogen that reacts, 72g of water is made.
8 of 13
What is the name given to atoms of the same element which has different mass numbers?
isotopes
9 of 13
These atoms have different numbers of which sub-atomic particle?
Neutrons
10 of 13
The relative atomic mass of a carbon 12 expressed in grams is called a ? of carbon atoms
mole
11 of 13
How is the formula mass of a compound calculated?
Adding up all the mass numbers of the elements in a compound from its formula
12 of 13
What is a reversible reaction
The products can react again to form the reactants
13 of 13

## Other cards in this set

### Card 2

#### Front

A scientist calculated that a reaction could be used to make 200g of sodium chloride. 175g was actually made. Work out the percetage yeild.

#### Back

actual yield is 175g, theoretical yeild is 200. 175/200x100=87.5% (percentage yeild)

### Card 3

#### Front

why do reactions rarely go to 100%?

#### Back ### Card 4

#### Front

What is chromatography?

#### Back ### Card 5

#### Front

what is gas chromatography?

#### Back 