CHEMISTRY, Moles, Chemical Calculations and yields

Question 1

Why are moles useful?

Answer 1

Atoms are too small to weigh individually so it’s easier to weigh a mole of something

Question 2

What is a mole?

Answer 2

a unit to measure the amount of a chemical we have

Question 3

What is the equation for the number of moles in a sample?

Answer 3

mass of the substance/Mr

Question 4

What is theoretical yield?

Answer 4

The expected amount of a product if all of our reactant is used

Question 5

What is the equation for percentage yield?

Answer 5

Actual yield produced/Theoretical yield of product x100

Question 6

Equation for percentage of atom economy?

Answer 6

Mr of the desired products / Mr of all reactants x100

Question 7

What is titration?

Answer 7

A technique that can be used to find out the concentration of an acid or an alkali.

Question 8

How can uncertainty be measured and how do you work it out?

Answer 8

By considering the resolution of the scientific equipment being used and from the range of the set of data. It’s the range/2

Question 9

What is Avogrado’s number?

Answer 9

6.02 x10 to the power of 23, number of particles in a mole.

Question 10

What happens when doing chemical calculations if the range gets larger?

Answer 10

More chance of error

Question 11

What are the tools needed in a titration practical?

Answer 11

pipette, burette, safety pipette filler, conical flask

Question 12

What is thermal decomposition?

Answer 12

A chemical reaction that happens when a compound is broken down when heated.

Question 13

What is the law of conservation of mass?

Answer 13

Matter can not be created or destroyed no matter how they are arranged.

Question 14

What is the equation for the concentration of a solution?

Answer 14

The amount of a substance/ The volume of the solvent

Question 15

What is the equation for working out moles of a gas?

Answer 15

Volume/molar gas volume (Vm)

Question 16

Why can we never have 100% yield in a reaction?

Answer 16

Other unexpected reactions can occur that don’t produce the desired product and sometimes not all of the reactants are used in the reaction.

Question 17

What is atom economy?

Answer 17

A measure of how many of the reactant atoms form a desired product.

Question 18

What are the preparation steps before doing a titration practical?

Answer 18

1. pipette should be rinsed with deionised water.
   2.Safety pipette filler is used to draw up the solution until bottom of menicis is on line then poured into conical flask.
   3.Burette is rinsed and then filled with solution ensuring the jet is filled.

Question 19

What is the method for the titration practical.

Answer 19

1. Use the pipette and pipette filler to add the sodium hydroxide to conical flask.
2. Add a few drops of indicator and put conical flask on white tile.
3. Fill burette with hydrochloric acid and note reading.
4. Add acid from burette to the conical flask and mix it.
5. Stop adding acid when the indicator changes colour and then repeat the steps until the concordant titres.