C4 - Chemical Calculations

Question 1

What is Avogadros constant?

Answer 1

One mole of a substance contains 6.02 x 10*23 atoms

Question 2

What is the equation triangle for Moles, Relative mass and mass

Answer 2

. Mass m
—————– ———–
Moles | Relative Mo | Mr
Mass

Question 3

How do you calculate the pecentage yield?

Answer 3

actual yield
————————- x 100
Theoretical yield

Question 4

How would you calculate the atom economy?

Answer 4

Mr of useful product
——————————- x 100
Mr of all reactants

Question 5

What is the unit for concentration?

Answer 5

g/dm*3

Question 6

How do you calculate concentration?

Answer 6

Mass (g)
————————- = Concentration (g/dm3)
Volume (dm3)

Question 7

How do you calculate the volume in dm3 from cm3?

Answer 7

Volume(cm3) / 1000 = Volume (dm3)

Question 8

How much cm are in 1 dm?

Answer 8

1000 cm

Question 9

What is the limiting reagent?

Answer 9

The reactant that runs out

Question 10

What is the excess in a reactant?

Answer 10

The reactant that is left over

Question 11

Solve this question.
What mass of oxygen reacts with 12g of magnesium?

2Mg + O2 —–> 2MgO

workout by hand

Answer 11

8g

Question 12

How do you find the number of MOLES in a given mass?

Answer 12

Number of Moles = mass in g / Mr

Question 13

What does does not happen to the atoms during chemical reaction that many get confused about?

Answer 13

In a chemical reaction, No atoms are destroyed and no atoms are created

Question 14

What must you do to ‘Show that a mass is conserved in a given reaction’ ?

Answer 14

Prove the reactant Mr is equal to the product Mr

Question 15

When do reactions stop?

Answer 15

When one reactant is used up

Question 16

What is the relationship to the limiting reactant and product formed?

Answer 16

The amount of product formed is directly proportional to the amount of limiting reactant

Question 17

How much decimetres does one mole of any gas at 20°C occupy?

Answer 17

24dm°3

Question 18

What is the equation to find out the volume of any gas at room temperature?

Answer 18

Volume of gas = Mass of gas / Mr of gass X 24

Question 19

How do you calculate the concentration of a solution with the given mass of the solute?

Answer 19

Concentration = mass of solute / volume of solvent

Question 20

How do you calculate the concentration of a solution with the given moles of the solute?

Answer 20

Concentration = number of moles of solute / volume of solvent

Question 21

What would 100% atom economy mean?

Answer 21

All the atoms in the reactants have turned into useful products

Question 22

The higher the atom economy, the ____________ the process

Answer 22

Environmentally friendly

Question 23

What are the benefits of higher atom economy?

Answer 23

Better for profits
Better for the environment

Question 24

What does the percentage yield tell you?

Answer 24

The overall success of an experiment

Question 25

What does the percentage yield compare?

Answer 25

The theoretical yield and the actual yield
(What you think you should get with what you actually get)

Question 26

What is a yield?

Answer 26

The amount of product you get

Question 27

Why are yields always less than 100%?

Answer 27

Some product or reactant can get lost in the reaction