🔥Chemistry 1.7 -equilibrium and Acid Based Reactions

Question 1

Define a reversible reaction

Answer 1

A reaction that can go in either direction depending on the conditions

Question 2

Define dynamic equilibrium

Answer 2

When the forward and reverse reactions occur at the same rate

Question 3

Define position of equilibrium

Answer 3

The proportion of products to reactants in an equilibrium mixture

Question 4

Define Le Chateliers principle

Answer 4

States that if a system at equilibrium is subjected to a changes, the equilibrium tends to shift so as to minimise the effect of change

Question 5

Define an acid

Answer 5

A proton (H+) donor

Question 6

Define a base

Answer 6

A proton (H+) acceptor

Question 7

Define a strong acid

Answer 7

An acid that fully dissociated in Aqueous solution.

Question 8

Define a weak acid

Answer 8

An acid that only partially dissociated in aqueous solution

Question 9

Define a salt

Answer 9

A compound that forms when a metal ion replaces the hydrogen ion in an acid

Question 10

Define a standard solution

Answer 10

One whose concentration is accurately known

Question 11

Name examples of reversible reactions

Answer 11

H2O (l) -<> H2O (s)

N2 (g) + 3H2(g) -<> 2NH3 (g) harbour process

Question 12

What are the 2 main types of equilibrium

Answer 12

Static and dynamic equilibrium

Question 13

Name an example of dynamic equilibrium

Answer 13

Dissolving copper sulfate crystals in water, the more added the deeper the blue colour until saturated where color remains constant, at this point the copper sulfate is dissolving at the same rate as the copper sulfate is recrystallising.

Question 14

What does the phrase “gone to completion” mean?

Answer 14

When an equilibrium mixture contains mostly products and hardly any reactants

Question 15

Define equilibrium mixture

Answer 15

The balance of reactants and products at equilibrium

Question 16

What do you deduce if the equilibrium mixture consists of mostly reactant and hardly any products

Answer 16

The reaction doesn’t occur under such conditions

Question 17

What are the features of equilibrium?

Answer 17

• dynamic at molecular level
• forebears and reverse reactions occur at the same rate
• closed system
• macroscopic properties remain constant

Question 18

What happens when an equilibrium is established

Answer 18

The concentrations of products and reactants reach steady values

Question 19

Describe how concentration affects equilibrium

Answer 19

If concentration is reactant is increased, the position of equilibrium moves to the right and more products are formed (opposite for if concentration decreases e.g adding water)

Question 20

Describe how pressure affects the position of equilibrium

Answer 20

Increasing pressure moves the position of equilibrium to whichever side of the equation has fewest moles, forming more of that substance (reverse for if you decrease pressure)

Question 21

Describe the effect of temperature on the position of equilibrium

Answer 21

An increase in temperature moves the position of equilibrium in endothermic direction. (Where there’s a (+^H)
-a decrease in temperature moves position in exothermic direction (-^H)

Question 22

What is the equilibrium constant represented by?

Answer 22

Kc
Where c indicates it is a ration of concentrations
Products/Reactants

Question 23

Name the general symbolism for an equilibrium

Answer 23

aA + bB -<> cC + dD
Where Kc = C to the power of c x D to the power of d/ A to the power of a x B to the power of b
(Products/Reactants)

Question 24

How to calculate the units for Kc?

Answer 24

(Mol dm -3) for each of the powers present In products/ reactants, than cancel
(CHECK PG 66 of textbook)

Question 25

When does the value of Kc shift to the right?

Answer 25

Where there’s a large numerical value of Kc as there are more products than reactants in the mixture

Question 26

When does the value of Kc shift to the left.

Answer 26

When Kc<1 because there are more reactants than products in the mixture

Question 27

What can Change the value of Kc? | What can’t change the value of Kc?

Answer 27

Only temperature can change the value of Kc as Kc is constant for a particular equilibrium at a constant temperature Changing pressure and concentration changes position of equilibrium, it does not hanged value of Kc

Question 28

What is an alkali?

Answer 28

A base which dissolves in water

Question 29

What is the ion common to all alkalis

Answer 29

OH-

Question 30

Name some examples of common bases

Answer 30

Magnesium oxide MgO Calcium oxide CaO Sodium hydroxide NaOH Ammonia NH3

Question 31

What is the general equation for the dissociation of an acid?

Answer 31

HA (aq) -<> H+ (aq) + A- (aq)

Question 32

Name an example of a weak and strong acid

Answer 32

``` Strong= HCL(aq) Weak = ethanoic acid CH3CO2H (aq) ```

Question 33

Show ethanoic dissociating

Answer 33

CH3CO2H (aq) -<> CH3CO2-(aq) + H+ (aq)

Question 34

What is pH defined as?

Answer 34

pH= -log(H+) | Where (H+) is the concentration of H+ in mol dm-3

Question 35

Why is the ‘-‘ sign in the pH equation vital

Answer 35

Because it results in pH decreasing as the aquarium hydrogen ion concentration increases

Question 36

How do you calculate the concentration of hydrogen ions from a pH?

Answer 36

Click shift log, then type in the negative pH E.g pH 2 has a hydrogen ion concentration of 0.01

Question 37

What does neutralisation always produce?

Answer 37

A salt, formed just by adding any insoluble base or carbonate but titration must be used for forming salts from alkalis as they’re soluble

Question 38

What colour change occurs with phenolphthalein and methyl orange (used in double titrations)

Answer 38

Phenolphthalein changes colour around pH 9 (pink to colourless) Relates to concentration of hydroxide and the carbonate Methyl orange changes colour around pH4 (yellow to orange) Relates to colour change of the carbonate only