Reactivity 2.1

Question 1

What occurs in a chemical reaction?

Answer 1

No overall change in mass. Energy change due to reactant bonds broken and new bonds formed.

Question 2

Relationship between reactant particles and number of product particles

Answer 2

It is fixed (known as stoichiometry)

Question 3

Ionic equations

Answer 3

Used to show the ions that react and the spectator ions that are left out.

Question 4

Half equation

Answer 4

When a change in oxidation state occurs, it can be useful to write the half equation

Question 5

Gas volume is determined by…

Answer 5

The number of particles and the temperature/pressure

Question 6

Avogadro’s Law

Answer 6

Equal volumes of the same gas under the same conditions of temperature and pressure contain equal numbers of molecules

Question 7

Molar volume

Answer 7

Volume occupied by one mole of gas. It is the same for all gases when measured under the same temp/pressure

Question 8

The concentration of a solution can be calculated by…

Answer 8

Titrating it with a standard solution with a known concentration

Question 9

cm^3 -> dm^3

Answer 9

/ 1000

Question 10

cm^3 -> m^3

Answer 10

/ 1000 /1000

Question 11

When is a back titration used?

Answer 11

Used when the end point is hard to identitfy or when one reactant is impure

Question 12

Back titration

Answer 12

A known excess of one of the reactants is added to the reaction mixture. Unreacted excess is determined by the titration against the standard solution. By subtracting the amount of unreacted reactant from the original amount used, the reacting amount can be determined.

Question 13

All gases under the same condition…

Answer 13

Have the same molar volume

Question 14

The mole ratio of an equation can be used to determine…

Answer 14

The concentrations of reactants and products in solutions

Question 15

Summary of how to solve an equation

Answer 15

• Write a balanced equation
  -For the given reactant find n (n=cv)
• Use the answer and mole ratio to find moles of other reactant
• Calculate c using c=n/V

Question 16

Limiting regeant

Answer 16

The reactant that runs out first - this determines the amount of product formed

Question 17

Theoretical yield

Answer 17

Maximum amount of product that could be formed according to the balanced equation

Question 18

Experimental yield

Answer 18

Actual amount of product obtained when experiment is preformed

Question 19

Percentage yield

Answer 19

(Experimental yield/theoretical yield) x 100

Question 20

Why would the experimental yield be lower than the theoretical? (5)

Answer 20

• Incomplete reaction
• Reversible chemical reactions preventing process completion
• Side reactions occurring
• Decomposition of reactants or products
• Loss of product during purification

(IRS DL)

Question 21

Why would the experimental yield be higher than the theoretical yield?

Answer 21

• Impurities in a product
• When a product has not been fully dried

Question 22

Standard solution

Answer 22

Solution of known concentration

Question 23

Acid-base titration

Answer 23

Titrated against a standard solution to determine concentration. When indicator changes colour, indicates the equivalence point

Question 24

Equivalence point

Answer 24

Where the stoichiometric amounts of acid and base have reacted completely

Question 25

Green chemistry

Answer 25

Seeks to minimise production and release to the environment of hazardous substances

Question 26

Formula for atom economy

Answer 26

= (mass of desired product/mass of actual products) x 100

Question 27

Atom efficient reactions

Answer 27

Addition polymerisation and hydrogenation of alkenes (high yield, no solvents, no by-products)