1.2 amounts of substance part 2

Question 1

what does stoichiometry tell you

Answer 1

the relative number of moles of reactant and products involved in a reaction

Question 2

what is stoichiometry found from

Answer 2

the balanced equation

Question 3

what is volumetric analysis used for

Answer 3

to find the volume of one solution which is needed to react with a measured volume of another solution

Question 4

what can the results of volumetric analysis be used to find

Answer 4

the unknown concentration of one of the solutions

Question 5

what is the solution with the known concentration called

Answer 5

the standard solution

Question 6

the 4 steps to making a standard solution:

Answer 6

dissolve known mass of solid in de-ionised water

using a funnel, transfer into a volumetric flask; include washings

make up to the graduated line by carefully adding de-ionised water, making sure the meniscus sits on the line

stopper the flask and invert to mix the contents thoroughly

Question 7

how to find the concentration of a solution of base

Answer 7

fill a burette with a known concentration of the acid

pipette a known volume of base into a conical flask

add a few drops of indicator to the base in the flask

add the solution of the acid from the burette until the indicator just changes colour- known as end point

record volume of acid added to nearest 0.05cm cubed
perform a rough titration and then sufficient accurate ones until the titres are concordant (within 0.01cm cubed of eachother)

calculate the mean titre from concordant titres to 2 d.p.

Question 8

what colour is methyl orange in acid

Answer 8

red

Question 9

what colour is methyl orange in base

Answer 9

yellow

Question 10

what is methyl orange’s end point colour

Answer 10

orange

Question 11

what colour is phenolphthalein in acid

Answer 11

colourless

Question 12

what colour is phenolphthalein in base

Answer 12

pink

Question 13

what is phenolphthalein’s end point colour

Answer 13

colourless

Question 14

What are acid base titration calculations used for

Answer 14

To find the concentration of a solution of the volume of solution which reacts

Question 15

What is a hydrated salt

Answer 15

A salt which contains water

Question 16

What happens when hydrated salts are heated

Answer 16

The water is driven off and the compound is said to be anhydrous

Question 17

What does waters of crystallisation refer to

Answer 17

The water molecules which form an essential part of the crystalline structure of a hydrated salt

Question 18

How to calculate the number of moles of water of crystallisation

Answer 18

• you will need to know the masses of the hydrated and anhydrous salts
• mass of water = mass of hydrated salt - mass anhydrous salt
• work out the number of moles of anhydrous salt and of water
• find the simplest whole number ratio

Question 19

What is percentage yield

Answer 19

A measure of the success of a laboratory preparation

Question 20

How to work out percentage yield

Answer 20

Actual yield of product/theoretical yield of product x 100

Question 21

Do both values need to be in moles for the percentage yield formula

Answer 21

Yes

Question 22

What is theoretical yield

Answer 22

The number of moles expected if the reactants were completely converted into products

Question 23

How to work out theoretical yield

Answer 23

Calculating the number of moles of reactants used and then using the balanced equation to calculate the number of moles of product if the yield was 100%

Question 24

What is actual yield

Answer 24

The actual number of moles of product formed in the reaction

Question 25

What is atom economy

Answer 25

A measure of the efficiency of a reaction in terms of the atoms involved

Question 26

What does atom economy consider

Answer 26

Desired product and by products

Question 27

Atom economy equation

Answer 27

Mr of desired product/sum of Mrs of all products x 100

Question 28

What can atom economy be calculated from

Answer 28

The balanced equation

Question 29

What is atom economy’s significance in terms of the environment

Answer 29

Lots of waste products

Question 30

Addition reaction

Answer 30

Have an atom economy of 100%- one product made

Question 31

Substitution and elimination reactions

Answer 31

Have an atom economy of less than 100%- at least 2 products made

Question 32

What is sustainable chemistry

Answer 32

The design of chemical products and processes that reduce the use of hazardous substances and generation of waste

Question 33

What does sustainability mean

Answer 33

Developing industrial processes that prevent the depletion of the earths natural resources

Question 34

Rules for chemical sustainability

Answer 34

1. Reduce use of hazardous chemicals
2. Reduce amount of waste
3. Recycle waste
4. Use fewer chemicals
5. Design for energy efficiency i.e. Use s catalyst and renewable energy resource
6. Use renewable feedstocks
7. Manufacture biodegradable products
8. Think safety
9. Establish international cooperation

Question 35

What are the downsides of green chemistry

Answer 35

1. Cost- research = people = £
2. Reduction of land needed for food
3. Adhering to international agreements