Quantative Chemistry

Question 1

How do you find relative formula mass?

Answer 1

Look at atomic mass on the periodic table

Question 2

How do you find mass of an element in a compound?

Answer 2

Ar X no. of atoms of that element
———————————————— X100
Mr of the compound

Question 3

What is Avogadro’s number?

Answer 3

6.02X 10*23

Question 4

How much mass does one mole of carbon have if it has a relative atomic mass of 12?

Answer 4

12g

Question 5

How do you work out the no. of moles?

Answer 5

mass in g/ Mr

Question 6

When will mass increase?

Answer 6

Gas is a reactant
Before the reaction it is floating in the air therefore it is not contained
When a gas reacts it becomes part of the reaction vessel

Question 7

When will mass decrease?

Answer 7

Gas is a product

If the vessel isn’t enclosed then the gas can escape

Question 8

How do you balance equations using reacting masses?

Answer 8

Divide each mass by its Mr to get no. of moles
Divide no. of moles by the smallest no. of moles
Then write a balanced symbol equation

Question 9

What is the reactant that is used up called?

Answer 9

Limiting reactant

Question 10

What is the amount of limiting reactant directly proportional too?

Answer 10

Amount of product formed

Question 11

How much does one mole of gas occupy at room temperature?

Answer 11

24dm*3

Question 12

How do you find volume of a gas?

Answer 12

Mass of gas
————————- X 24
Volume of solvent

Question 13

How do you find concentration in g/dm*3?

Answer 13

mass of solute/ volume of solvent

Question 14

How do you find concentration in mol/dm*3?

Answer 14

no. of moles of solute/ volume of solvent

Question 15

How do you convert from mol/dm3 to g/dm3?

Answer 15

mass= moles X Mr

Question 16

How do you convert from g/dm3 to mol/dm3?

Answer 16

moles= mass/Mr

Question 17

How do you find atom economy?

Answer 17

Mr of desired product
——————————– X100
Mr of all reactants

Question 18

What does 100% atom economy mean?

Answer 18

All reactants have been turned into the desired product

Question 19

If the atom economy what does that mean the process is?

Answer 19

“Greener”

Question 20

How do you find percentage yield?

Answer 20

mass of product made
———————————————- X100
max theoretical mass of product

Question 21

Why are yields always less than 100%?

Answer 21

As some products or reactants always get lost

Question 22

What are the reasons for product or reactant always being lost?

Answer 22

Reactants will all not react to make a product
There may be a side reaction
You lose some product when you separate it from the reaction mixture

Question 23

Why in a reversible reaction will there never be 100% yield?

Answer 23

Because products can turn back into reactants

Question 24

Why does side reactions cause not 100% yield?

Answer 24

May react with gases in the air or impurities to form extra products

Question 25

How do you lose some product when you separate?

Answer 25

If you filter a liquid you remove some solid particles

Lose bits of the liquid that remains with the solid on the filter paper