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as chemistry > 1.7 - Simple Equilibria and Acid-Base Titrations > Flashcards

1.7 - Simple Equilibria and Acid-Base Titrations Flashcards

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1
Q

What is a reversible reaction?

A

One that can go in either direction depending on the conditions.

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2
Q

What is a dynamic equilibrium?

A

When the foward and reverse reactions occur at the same rate.

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3
Q

What is Le Chatelier’s principle?

A

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

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4
Q

What happens when the conc of a reactant is increased?

A

The position of equilibrium shifts to the right and more products are formed.

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5
Q

What does the pressure of a gas depend on?

A

The number of molecules in a given gas.
The greater the number of molecules, the greater the number of collisions per unit time, therefore the greater the pressure of gas.

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6
Q

What does high pressure mean on an equilibrium system?

A

high pressure = higher amount of moles on one side
Increasing the pressure moves the position of the equilibrium to whichever side of the equation has fewer gas molecules.

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7
Q

What is meant by ‘endothermic’?

A

Absorbing heat from surroundings (positive)

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8
Q

What is meant by ‘exothermic’?

A

Gives out heat to surroundings (negative)

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9
Q

What reaction is it if enthalpy change is positive?

A

The foward reaction is endothermic

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10
Q

What reaction is it if enthalpy change is negative?

A

The foward reaction is exothermic

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11
Q

What do catalysts do?

A

Speeds up a chemical reaction by lowering the activation energy of the reaction. Does not effect the position of the equilibrium, but equilibrium is reached faster.

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12
Q

How does a catalyst effect a reversible reaction?

A

A catalyst will increase the rate of the foward reaction and backward reaction to the same extent.

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13
Q

What is an equilibrium constant?

A

The position of equilibrium in a reversible reaction may be described in precise terms by combining the equilibrium concentrations to give a value.
GIven the symbol Kc (where c indicates ratio for concentration)

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14
Q

What is the equation for equilibrium constant?

A

aA + bB = cC + dD
Kc = (C)c(D)d/(A)a(B)b
Kc = products/reactants
Conc is raised to number of moles in equation.
Units should be moldm-3

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15
Q

What is an acid in terms of protons?

A

Acids are proton (H+) donors

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16
Q

What is a base in terms of protons?

A

Bases are proton (H+) acceptors

17
Q

What is the process of dissociating?

A

Acids donating H+ ions in an aqueous solution.

18
Q

Name 4 common acids.

A

Hydrochloric acid HCl
Sulphuric acid H2SO4
Nitric acid HNO3
Ethanoic acid CH3COOH

19
Q

Name 4 common bases.

A

Magnesium oxide MgO
Sodium hydroxide NaOH
Calcium oxide CaO
Ammonia NH3

20
Q

What is meant by a concentrated acid?

A

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

21
Q

What is meant by a dilute concentrated acid?

A

A dilute acid contains a large quantity of water and a small quantity of acid.

22
Q

How can you measure the acidity of a solution?

A

Measured by the concentration of aqueous hydrogen ions.

23
Q

What is the equation for pH?

A

pH = -log10 (H+)
(where H+ is concentration in mol dm-3)
(the negative sign is pH decreasing as H+ increases, if concentration is greater than 10-7 mol dm-3, the pH is less than 7)

24
Q

Where are acids on the pH scale?

A

0-6 red, orange, yellow

25
Q

What is considered neutral on the pH scale?

A

7 green

26
Q

Where are alkalis on the pH scale?

A

8-14 blue, dark blue, purple

27
Q

What are the 3 types of titrations?

A

Acid/base titration, back and double.

28
Q

What are the 3 key apparatus for a titration?

A

Burette, pipette and conical flask

29
Q

What counts as an accurate result for a titration?

A

At least 2 titres within 0.20cm^3 of eachother are required
Use titres within 0.20cm^3 for mean calculations.

30
Q

What is a back titration?

A

A back titration is where the concentration of an unknown compound is determined by reacting with a known amount of excess reagent.

31
Q

What is a double titration?

A

Finding out 2 unknown concentrations in a solution through use of 2 different indicators.

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