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Science Chemistry > C7, C8 > Flashcards

C7, C8 Flashcards

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1
Q

bond making is:

A

exothermic

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2
Q

the effect of pressure

A
  • increasing the pressure increases the frequency of collisions
  • so increases the rate of reaction
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3
Q

collision theory:

A
  • particles collide all the time, but only some lead to reactions
  • increasing the number of collisions produces faster rates of reactions
  • larger surface area increases the frequency of collisions.
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4
Q

reaction profile for exothermic reactions:

A

-the products are at a lower energy level than the reactants.

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5
Q

energy and reversible reactions

A
  • one reaction is exothermic and the other is endothermic
  • the amount of energy transferred to the surroundings in one direction is exactly equal to the the energy transferred back in the other direction
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6
Q

energy is conserved in chemical reactions. It is neither created nor destroyed

A

energy is conserved in chemical reactions. It is neither created nor destroyed

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7
Q

endothermic reaction examples:

A
  • citric acid and sodium hydrogencarbonate

- decomposition of calcium carbonate

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8
Q

surface area:

A
  • if the surface area to volume ratio of any solid reactants increases the rate of a reaction increases.
  • this increases the frequency of collisions between reacting particles
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9
Q

how can you represent reversible reactions?

A

-using the sign with one arrow pointing forwards and one pointing backwards.

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10
Q

reaction profile for endothermic reactions:

A

-the products are at a higher energy level than the reactants.

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11
Q

exothermic changes use:

A
  • hand warmers

- self-hearing cans

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12
Q

explain the experiment for hydrochloric acid(required practical)

A

place 1 g of marble chips(calcium carbonate) in a chronicle flask of 50 cm³ of hydrochloric acid. Immediately placed the bung on the chronicle flask and record the…

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13
Q

what happens when the pressure is decreased in a reversible reaction? (le chatelier’s principle)

A

when pressure is decreased, volume is increased and makes a shift to the left with more moles of gas

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14
Q

the activation energy is:

A

the minimum amount of energy needed to start a reaction

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15
Q

what happens if we remove the heat from the reversible reaction? (le chatelier’s principle)

A

if heat is removed we shift to the right

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16
Q

the effect of temperature:

A
  • as temperature increases reactions happen more quickly

- increasing temp increases the rate of reaction because particles collide more frequently and more energetically

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17
Q

dynamic equilibrium

A
  • in a closed system, the rate of the forward and reverse reactions is equal at equilibrium.
  • changing reaction conditions can change the amount of products and reactants in a reaction mixture at equilibrium
18
Q

catalyst examples

A
  • iron to make ammonia

- platinum to make nitric acid

19
Q

define equilibrium

A

the state in which both reactants and products are present in concentrations which have no further tendency to change with time

20
Q

what is a reaction in which energy is transferred to the reacting substance from their surroundings called?

A

endothermic

21
Q

what is a reversible reaction?

A

-a reaction where the products can react to make the original reactants

22
Q

main factors which affect the rate of chemical reactions:

A
  • temperature
  • surface area of solids
  • concentration of solutions or pressure of gases
  • presence of a catalyst
23
Q

altering conditions (pressure)

A
  • increasing the pressure favours the reaction that forms fewer molecules of gas.
  • decreasing the pressure favours the reaction that forms the greater number of molecules of gas

(changing pressure affects the equilibrium only if there are different numbers of molecules of gases on each side of the balanced equation)

24
Q

what happens when nitrogen or hydrogen is added to the reversible reaction? (le chatelier’s principle)

A

if you add nitrogen or hydrogen the equilibrium shifts to the right or towards the products

25
Q

how can u find the rate of reactions?

A
  • by monitoring the amount of reactants used up over time

- by measuring the amount of products made over time

26
Q

catalysts uses in industry

A
  • increase rates of reaction
  • reduce energy costs
  • catalysts are expensive, but it is usually cheaper to use a catalyst than to pay for the extra energy needed without one
27
Q

the effect of catalysts

A
  • a catalyst speeds up the rate of a reaction

- different catalysts are needed for different reactions

28
Q

endothermic changes use:

A

-instant cold packs for sports injuries

29
Q

the effect of concentration

A
  • increasing the concentration of reactants increases the frequency of collisions between particles
  • so increases the rate of reaction.
30
Q

what does le chatelier’s principle state?

A

le chatelier’s principle states that if you somehow change a system at equilibrium, it will shift left or right to partically offest the change

31
Q

what happens when heat is added to the reversible reaction? (le chatelier’s principle)

A

if heat is added to the reaction we shift to the left

32
Q

to work out the mean rate of reaction

A

quantity of reactant used/time
Or
quantity of product formed/time

33
Q

what would happen if we added ammonia to the reversible reaction? (le chatelier’s principle)

A

if you added ammonia to the right hand side of the equilibrium shifts to the left

34
Q

altering conditions(temperature and equilibrium)

A
  • increasing temp favours the endothermic reaction

- decreasing temp favours the exothermic reaction

35
Q

what is a reaction where u can measure a fall in temperature called?

A

endothermic

36
Q

bond breaking is:

A

endothermic

37
Q

how can u make sure the experiment is fair? (magnesium and solution concentration)

A
  • clean test tube
  • same volume of solution
  • same mass and surface area
38
Q

exothermic reaction examples:

A
  • combustion of methane gas

- neutralisation between acids and alkalis

39
Q

what is a reaction in which energy is transferred from the reacting substances to their surroundings called?

A

exothermic

40
Q

what is a reaction where u can measure a rise in temperature called?

A

exothermic

41
Q

actual yeild definition

A

the amount of product obtained in a chemical reaction

Science Chemistry (5 decks)

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