Volumetric analysis

Question 1

in an experiment why would no stopper be used

Answer 1

to allow gas to escape

Question 2

Why should deionised or distilled water be used rather than tap water

Answer 2

impurities may be present in tap water

Question 3

Describe how a burette should be prepares and set up ready to begin a titration

Answer 3

rinse the burette with the required solution
fill burette above the scale with the solution
filter funnel used should be removed
reading should be taken from the bottom of the meniscus

Question 4

suggests why the activation energy for a reaction may be low

Answer 4

the reaction is spontaneous

Question 5

Suggests points of good practice that a student should follow to ensure an accurate end point is achieved in a titration

Answer 5

all readings taken at eye level
All glassware is clean and has been rinsed with the solution to be used.
White paper under the flask to easily identify the end-point.

Question 6

Describe how a test using fehlings or benedicts solution should be carried out

Answer 6

Sample and Benedict’s solution in a test tube in a hot water bath

Question 7

Describe how to set up an enthalpy of combustion reaction

Answer 7

measure temperature of water at the start
weight the fuel at the start
burn the fuel then extinguish the flame
measure the maximum temperature
weight the fuel at the end

Question 8

How to make up a standard solution

Answer 8

weigh mass of solute
dissolve in small volume of deionised water in a beaker
transfer to standard flask with repeat rinsings
fill flask with deionised water until the bottom of the meniscus is line marked
stopper and invert to mix

Question 9

What is the most accurate piece of equipment to measure volume

Answer 9

pipette

Question 10

Why would gas be collected over water

Answer 10

insoluble gases
where a dry sample is not required

Question 11

Why would gas be collected using a gas syringe

Answer 11

soluble gases
where a dry sample is required

Question 12

What is a titration used for

Answer 12

accurately determine the volume of solution required to reach the end point of a chemical reaction

Question 13

suggest a disadvantage of using a methanol fuel cell when compared to a hydrogen fuel cell

Answer 13

the use of methanol as a fuel would produce carbon dioxide

Question 14

Give reasons why a process is profitable

Answer 14

low cost of reactants
exothermic reaction so the energy released could be used in other processes
costs are less as low pressure is used

Question 15

Explain why the relative rate of a reaction decreases as the concentration of the solution decreases

Answer 15

fewer collisions are taking place as concentration decreases

Question 16

What piece of glassware is used to prepare a standard solution

Answer 16

volumetric flask

Question 17

Describe how a 250cm of a standard solution would be prepared

Answer 17

dissolve in small volume of deionised water
transfer with rinsing up to the line in a standard flask

Question 18

What is filtration

Answer 18

used to separate a solid reside from a liquid or a solution

Question 19

In an experiment to measure the rate of reaction, which piece of equipment is used to collect gas evolved?

Answer 19

gas syringe

Question 20

State the measurements required to calculate the mass of an alcohol burned in an enthalpy of combustion reaction

Answer 20

mass of burner before and mass of burner after

Question 21

What is the end point of a titration

Answer 21

the point where the reaction has just reached completion

Question 22

Describe fully a method to accurately measure the mass of a 10.0 cm solution

Answer 22

Use a 10cm3 pipette to transfer the solution to a beaker that has been tared on a balance

Question 23

how can a gas that is insoluble in water be collected

Answer 23

displacement of water

Question 24

To ‘transfer quantitatively’ means that all of the iron tablet solution must
be transferred into the volumetric flask.
Describe how this is carried out in practice.

Answer 24

Rinse beaker and transfer the rinsing’s to the flask

Question 25

What is an indicator

Answer 25

a substance which changes colour when a reaction is just complete

Question 26

What is the correct way to measuring the mass of a solid

Answer 26

weighing by difference

Question 27

Describe a procedure to accurately weigh out a 50·0 g sample of iodised table salt.

Answer 27

Set the balance to zero, place weighing bottle on balance. Record empty mass. Add 50.0g of salt to weighing bottle on balance and record the new mass. The difference in masses is the mass of the substance in the bottle.

Question 28

What is the burette used for in a titration

Answer 28

gradually and accurately add small volumes of solution to the conical flask

Question 29

Suggest ways to maximise profit in an industrial process

Answer 29

recycle gases use a catalyst using the by products

Question 30

Explain why the aluminium foil needs to be heated at the start of the preparation, despite the reaction being highly exothermic.

Answer 30

To provide the activation energy

Question 31

What is a condensation reaction

Answer 31

two small molecules join together to form a larger molecule with the loss of water

Question 32

Why would tap water not be used when making a standard solution

Answer 32

it contains metal ions that could alter the concentration

Question 33

What does transfer quantitively mean

Answer 33

transfer with repeat rinsings

Question 34

Describe how to form a solution

Answer 34

use pipette to measure volume required and transfer directly into standard flask fill flask with deionised water until bottom of the meniscus is on the marked line stopper and invert to mix

Question 35

Suggest why fuel cells are thought to be more environmentally friendly than aviation fuels

Answer 35

water is the only product

Question 36

Name factors that are important influences on the design of an industrial process

Answer 36

opportunities for recycling marketability of by products product yield

Question 37

Give a reason for titrating several smaller samples of fruit drinks

Answer 37

improve reliability

Question 38

What are the environmental consideration in an industrial process

Answer 38

minimising waste avoiding the use of toxic substances designing products which will biodegrade if appropriate

Question 39

Explain the steps to collect, dry and weigh a precipitate

Answer 39

weigh the filter paper filter the precipitate wash the precipitate with water to remove any impurities dry the precipitate in the oven weigh the precipitate and the filter paper

Question 40

Suggest why between two methods one is the preferred industrial route

Answer 40

it has 100% atom economy there is only one product

Question 41

State variables that must be kept constant during a enthalpy of combustion experiment

Answer 41

Distance between flame and beaker Beaker made of same material Same draught proofing

Question 42

Describe how a pipette should be prepared and used to accurately measure the sample of seawater

Answer 42

Rinse with seawater/solution Fill to mark and read from the bottom of the meniscus

Question 43

What is volumetric analysis

Answer 43

involves using a solution of known concentration to determine the concentration of another substance

Question 44

how do you separate liquids or gases from each other

Answer 44

evaporation