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chemistry > Thermochemistry > Flashcards

Thermochemistry Flashcards

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0
Q

What is an exothermic reaction?

A

A reaction where heat is given out

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1
Q

What is thermochemistry?

A

Thermochemistry is the study of heat changes that take place during chemical reactions.

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2
Q

Is exothermic positive or negative?

A

Negative

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3
Q

Give an example of an exothermic reaction

A

Using a Bunsen burner

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4
Q

What is an endothermic reaction?

A

A reaction where heat is taken in

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5
Q

Is an endothermic reaction positive or negative?

A

Positive

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6
Q

Give an example of an endothermic reaction

A

Cooling packs

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7
Q

What conditions are necessary for exothermic reactions and endothermic reactions to take place?

A

Room temperature and pressure

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8
Q

What is the transition from solid to liquid called?

A

Melting

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9
Q

What is the transition from liquid to gas called?

A

Evaporating

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10
Q

What is the transition from gas to liquid called?

A

Condensing

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11
Q

What is the transition from liquid to solid called?

A

Freezing

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12
Q

What is the transition from solid to gas called?

A

Sublimation

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13
Q

In chemical reactions what must be supplied to break bonds?

A

Energy

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14
Q

When bonds are breaking energy is taken, this makes them…?

A

Endothermic

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15
Q

When bonds are forming energy is given out, this is known as….?

A

Exothermic

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16
Q

Name the least reactive alkali metal

A

Lithium (Li)

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17
Q

Name the most reactive alkali metal

A

Francium

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18
Q

Name all the alkali metals in order

A

Lithium, Sodium, Potassium, Rubidium, Cesium and Francium

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19
Q

What are the properties of Alkali metals?

A

Soft metal and low density

Li, Na and K float in water

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20
Q

When cut Alkali metals are exposed to air, a reaction takes place between the metal and oxygen. What do you notice about the metal?

A

It has a metallic shine

21
Q

What is formed when alkali metals burn in the air?

A

Metal oxide

22
Q

Sodium + Oxygen=

A

Sodium oxide

23
Q

Give the word equation for…

2Na + 2H2O ~ 2NaOH + H2

A

Sodium + water ~

Sodium Hydroxide + Hydrogen

24
Q

Give the chemical equation for…
Sodium + water ~
Sodiumoxide + Hydrogen

A

2Na + 2H2O ~ 2NaOH + H2

25
Q

Define the heat of combustion

A

Heat of combustion of a substance is the heat change in kilo joules when one mole of the substance is completely burnt in excess oxygen

26
Q

How can the heat of combustion be measured?

A

Using a bomb calorimeter

27
Q

Describe how the heat of combustion is carried out

A

A known amount of substance is placed in crubide. The bomb is then pressured with oxygen and placed in cold water. Temperature of cold water is measured. The sample is ignited. Once fully burned the water is stirred ( ensures uniform rise in temperature). The highest temp reached in the water is noted.

28
Q

What’s needed to combust a substance?

A

Oxygen

29
Q

What is formed after the combustion of a substance

A

Carbon dioxide and water

30
Q

Write the combustion equation of methane

A

CH4+O2->CO2+H2O

31
Q

Balance this combustion of methane equation

CH4+O2->CO2+H2O

A

CH4+2O2->CO2+2H2O

32
Q

In what order must hydrogen carbon and oxygen be balanced?

A

Carbon, hydrogen and oxygen

33
Q

What goes on the left hand side (LHS) of the combustion equation

A

The substance you’re reacting and oxygen

34
Q

What goes on the right hand side (RHS) of the combustion equation

A

Carbon dioxide and water

35
Q

Balance this combustion of Butane equation (C4 H10)

C4H10+O2->CO2+H2O

A

C4H10+6.5O2->4CO2+5H2O

36
Q

Balance this combustion of Pentane equation (C5 H12)

C5H12+O2->CO2+H2O

A

C5H12+8O2->5CO2+6H2O

37
Q

Balance this combustion of Hexane equation (C6 H14)

C6H14+O2->CO2+H2O

A

C6H14+9.5O2->6CO2+7H2O

38
Q

Balance this combustion of Hexane equation (C2 H4)

C2H4+O2->CO2+H2O

A

C2H4+3O2->2CO2+2H2O

39
Q

Define the heat of formation

A

The heat of formation is the heat change in kilo joules, when the mole of a substance is formed from its elements in their standard states

40
Q

Write the equation for the formation of ethane (C2 H4)

A

2C+2H2->C2H4

41
Q

Write the heat of formation of water (H2O)

A

H2+1/2 O2

42
Q

Write the equation for the formation of ethanol

A

2C+1/2 O2+3H2->C2H5OH

43
Q

Define the law of conservation of energy

A

Energy can not be created or destroyed but can be changed from one form to another.

44
Q

Give an example of the law of conservation of energy

A

Chemical energy->light energy

Chemical energy->heat energy

45
Q

Define the heat of reaction

A

The heat of reaction is the heat change that takes place according to a given reaction

46
Q

What is the formula to calculate heat change?

A

mc (triangle) T

47
Q

What is m?

A

Mass in kg

48
Q

What is c?

A

Specific heat capacity

49
Q

What is (triangle) T

A

Change in temperature

50
Q

What is Hess law?

A

Hess law states that the heat change of a reaction depends on the initial and final states of the reaction and is independent of the route by which the reaction may occur

chemistry (9 decks)

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