WJEC AS Chemistry Unit 1.7 - Simple Equilibria and Acid-Base Reactions

0.0(0)
studied byStudied by 0 people
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/16

flashcard set

Earn XP

Description and Tags

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

17 Terms

1
New cards

Reversible reaction

  • a reaction which can go in either direction depending on the conditions

  • when you have a reversible reaction in a closed system, a dynamic eqilibrium is reached

2
New cards

Dynamic Equilibrium

in a reversible reaction the rate of forward reaction is equal to rate of backward reaction

3
New cards

Equilibrium

  • rate of forward reaction=rate of backward reaction

  • changes occur on a molecular level only

  • concentration of all reactants and products remains constant, therefore no observable overall change

  • Conditions; to reach equilibrium, the reaction must be a closed system (all chemicals kept in), therefore rates of reaction equal

4
New cards

Position of Equilibrium

  • Proportion of products and reactants in an equilibrium mixture

  • Changed if conditions changed in a way which changes the rate of the forward or backward reactions

  • can be changed by changing the reaction conditions

  • Influenced by concentration, temperature and pressure

  • May result in colour change

  • Lies to the left = more reactants than products, therefore higher reactant concentration

  • Lies to the right = more products than reactants, therefore high product concentration

5
New cards

Le Chatelier’s Principle

If a system at equilibrium is subjected to a change then the position of equilibrium to shift to minimise/oppose that change

6
New cards

Effect of concentration change on equilibrium

  • Increase concentration of a reactant;

    • position of equilibrium will move so that the conc of this reactant decreases by reacting with other reactants and turning into products

    • position of equilibrium moves to the right

    • more products formed

  • Decreasing the concentration of a reactant;

    • position of equilibrium will move so that the conc of this reactant increases again

    • More products will react to replace the reactant that’s been removed

    • The position of equilibrium moves to the left

  • Increasing the concentration of a product;

    • moves to the left as it shifts to decrease the conc of prodycst

    • more reactancts formed

7
New cards

Effect of temperature on position of equilibrium

  • If enthalpy change is negative;

    • Reaction is exothermic

    • Temperature increase; position of equilibrium moves to the left

  • If enthalpy change is positive;

    • reactions is endothermic

    • Temperature increase; position of equilibrium moves to the right

  • An increase in temperature moves the position of the equilibrium in the endothermic direction

8
New cards

Effect of a catalyst on position of equilibrium

  • decreases time it takes to reach equilibrium by lowering the activation energy

  • increases rate of forward and backward reactions to the same extent

  • does not affect the position of equilibrium

9
New cards

Equilibrium Constant, Kc

  • Solids are never included

  • Not affected by pressure or concentration, only temperature

  • Use square brackets around formulae (represents conc in moldm^-3)

  • Units vary. Must state units. Can have not units

  • Greater value; the further the positions of equilibrium lies to the right

  • Smaller value; the further the positional of equilibrium lies to the left

<ul><li><p>Solids are never included</p></li><li><p>Not affected by pressure or concentration, only temperature</p></li><li><p>Use square brackets around formulae (represents conc in moldm^-3)</p></li><li><p>Units vary. Must state units. Can have not units</p></li><li><p>Greater value; the further the positions of equilibrium lies to the right</p></li><li><p>Smaller value; the further the positional of equilibrium lies to the left</p></li></ul><p></p>
10
New cards

Acids

  • Donors of H+ (aq)

  • can be described as strong/weak or concentrated/dilute

11
New cards

Bases

  • acceptors of H+ (aq)

  • When disolved in water, it is called an alkali. Common ion to all alkalis = hydroxide ion

12
New cards

Strong vs Weak Acid

  • A strong acid is fully dossociated/ionised in an aqueous solution. The more easily/quicker an acid can donate H+, the stronger the acid

  • A weak acid is only partially disscoiated in aqueous solution

13
New cards

Concentrated vs Dilute acid

  • A concentrated acid consists of a large quantity of acid and a small quantity of water

  • A dilute acid consists if a large quantity of water and a small quantity of acid

  • Possible to have a dilute solution of a strong acid or a concentrated solution of a weak acid

14
New cards

Monobasic acid

an acid that has 1 replacable hydrogen ion, such as HCl

Produces 1 mole of H+(aq) per 1 mole of acid

Hydrogen ion concentration = the concentration of the acid

15
New cards

Dibasic acid

An acid that has 2 replacable hydrogen ions such as H2SO4

Produces 2 moles of H+(aq) per 1 mole of acid

Hydrogen ion concentration =2x concentration of the acid

16
New cards

Relationship between pH and H+(aq) concentration

  • acidity of a solution; a measure of the conc of the aqueous hydrogen ion

  • pH=-log[H+] where [H+] is the conc of H+ in mol dm-3

  • [H+]=10^-pH

17
New cards

Acid-based titrations