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IGCSE CHEMISTRY REVISION > Chemical reactions Details > Flashcards

Chemical reactions Details Flashcards

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1
Q

Signs of a chemical change

A

-One or more new chemical substances are formed
-Energy is taken in/given out during the reaction
-Change is usually difficult to reverse

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2
Q

Signs of a physical change

A

-No new chemical substances are formed
-Change is usually easy to reverse

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3
Q

Factors which affect the rate of reaction

A

-Concentration
-Pressure
-Temperature
-Surface area(of reactants)
-Presence of catalyst

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4
Q

Why increased concentration increases the rate of reaction

A

-More particles per unit volume
-Higher collision rate
-Higher rate of reaction

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5
Q

Why increased pressure affects the rate of reaction

A

-Gas molecules are closer together
-Increased collision rate
-Increased rate of reaction

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6
Q

Why increased temperature affects the rate of reaction

A

-Particles have more energy and move faster
-Increased collision rate
-More particles have enough energy to start a reaction
-Increased rate of reaction

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7
Q

Why increased surface area affects the rate of reaction

A

-More particles exposed to other reactant
-Greater chance of particles colliding
-Increased collision rate
-Increased rate of reaction

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8
Q

Features of catalysts

A

-Increase the rate of reaction
-Is unchanged at the end of the reaction
-Decrease the activation energy of a reaction

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9
Q

A reversible reaction in a closed system is at equilibrium when…

A

-the rate of the forward reaction is equal to the rate of the reverse reaction
-the concentrations of reactants and products are no longer changing

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10
Q

Factors which affect the position of equilibrium(in a reversible reaction)

A

-Changing temperature
-Changing pressure
-Changing concentration
-Removing the product

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11
Q

Effect on yield if temperature is increased in a reversible reaction(forward reaction is exothermic)

A

temperature ↑ means yield ↓

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12
Q

Effect on yield if temperature is increased in a reversible reaction(forward reaction is endothermic)

A

temperature ↑ means yield ↑

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13
Q

If the pressure is increased(in a reversible reaction), the equilibrium moves…

A

in the direction of the fewest molecules of gas

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14
Q

When does a change in temperature shift equilibrium?

A

ALWAYS

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15
Q

When does a change in pressure shift equilibrium

A

When the reactants/products are gases and the number of molecules is different on each side of the equation

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16
Q

The Haber process is used for the…

A

production of ammonia

17
Q

Symbol equation for the Haber process

A

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

18
Q

Where hydrogen needed for the Haber process is obtained from

A

Methane

19
Q

Where nitrogen needed for the Haber process is obtained from

A

Air

20
Q

Typical conditions for the Haber process

A

-Temperature: 450°C
-Pressure: 20,000kPa/200atm
-Catalyst: iron

21
Q

The Contact process is used for the…

A

production of (concentrated)sulfuric acid

22
Q

Symbol equations for the Contact process

A

2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
H₂O(l) + SO₃(g) → H₂SO₄(l)

23
Q

Where sulfur dioxide needed for the Contact process is obtained from

A

-Burning sulfur
-Roasting sulfide ores

24
Q

Where oxygen needed for the Contact process is obtained from

A

Air

25
Q

Typical conditions for the Contact process

A

-Temperature: 450°C
-Pressure: 200kPa/2atm
-Catalyst: vanadium(V) oxide

26
Q

The temperature for the Haber/Contact process is chosen as it is…

A

-low enough to achieve an acceptable yield
-high enough to do this in an acceptable time

27
Q

The pressure for the Haber/Contact process is chosen as it is…

A

-low enough to keep costs down
-high enough to achieve an acceptable yield

28
Q

Potassium manganate(VII) is an(in terms of redox)…

A

oxidising agent

29
Q

Use of potassium(VII) manganate

A

Used to test for the presence of reducing agents

30
Q

In the presence of a reducing agent, the colour of potassium manganate(VII) changes…

A

from purple to colourless

31
Q

Potassium iodide is(in terms of redox)…

A

a reducing agent

32
Q

Use of potassium iodide

A

Used to test for the presence of oxidising agents

33
Q

When potassium iodide is added to an acidified solution of an oxidising agent(eg. hydrogen peroxide(H₂O₂), aqueous chlorine), the colour of the solution changes…

A

from colourless to brown(due to the formation of iodine(I₂)

IGCSE CHEMISTRY REVISION (8 decks)

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