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Chemistry ATAR > Moles > Flashcards

Moles Flashcards

1
Q

What is relative mass

A

Mass cannot be measured using standard units (Too small)

Relative masses compare mass to 1/12 mass of Carbon-12 atom (No units)

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2
Q

What is relative atomic mass

A

Relative mass of single atom (On periodic table)

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3
Q

What is relative molecular mass

A

Relative mass of molecule (Sum of relative atomic masses of molecule)

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4
Q

What is relative formula mass

A

Relative mass of formula unit of ionic / covalent network substance

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5
Q

What is a mole

A

Measure number of atoms / molecules / formula units

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6
Q

What is the value of 1 mole in particles

A

6.022 x 10^23 particles (Avogadro’s Number)

Amount of atoms in 12g of Carbon-12

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7
Q

What is the formula for amount of substance in mole

A

Amount of substance in mole = (Amount of particles of substance) / (Number of particles in 1 mole)

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8
Q

What is molar mass

A

Mass (g) of one mole of pure substance

Molar mass (g) = Relative mass (g)

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9
Q

What is formula for molar mass

A

Amount of substance in mole = (Mass of substance) / (Molar mass of substance)

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10
Q

What is percentage composition

A

Proportion by mass of different elements in compound

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11
Q

What is formula for percentage composition

A

% by mass of element in compound = (Mass of element in 1 mole of compound) / (Molar mass of compound) * 100%

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12
Q

What are chemical reactions

A

When particles collide, rearranged to form “new” substances

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13
Q

What are energy changes in chemical reactions

A

Reactions involve breaking of chemical bonds, formation of new ones

  • Breaking bonds require energy absorbed from surroundings
  • Formation releases energy to surroundings
  • Energy mostly heat, light, electricity (J, kJ, MJ)
  • Change in chemical energy (Energy stored in chemical bonds) due to reaction

– Is converted to other forms

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14
Q

What are phase changes either exothermic or endothermic

A

Liquid to gas = Endothermic, energy absorbed from surroundings

Liquid to solid = Exothermic, energy released to surroundings

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15
Q

What is the conservation of energy

A

Energy cannot be created or destroyed, only transferred or transformed

System is chemical reaction, energy absorbed / released by system

  • Absorbed / Released to surroundings (Eg. Air, Water, Container)
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16
Q

What is exothermic reactions

A

Releases energy to surroundings

17
Q

What is properties of exothermic reactions

A

Chemical energy of products < reactants

Energy absorbed < Energy released

Lost energy released to surroundings

Feels warm (Temperature change to surroundings positive)

18
Q

What is endothermic reactions

A

Absorb energy from surroundings

19
Q

What is properties of endothermic reactions

A

Chemical energy of products > reactants

Energy absorbed > Energy released

Added energy absorbed to surroundings

Feels cold (Temperature change to surroundings negative)

20
Q

What are chemical equations of exothermic reactions

A

Energy added to products

21
Q

What are chemial equations of endothermic reactions

A

Energy added to reactants

22
Q

What is enthalpy

A

Stored chemical energy of substance (J), symbol H

23
Q

What is heat of change

A

Amount of energy absorbed / released in chemical reaction

23
Q

What is enthalpy change

A

Exchange of heat between system & surroundings

Enthalpy change = Enthalpy of products - Enthalpy of reactants

23
Q

What is enthalpy change in exothermic reactions

A

Negative

24
Q

What is enthalpy change in exothermic reactions

A

Positive

25
Q

What are enthalpy diagrams

A

Graphically show change in enthalpy as reaction proceeds

26
Q

What are bond enthalpies

A

Breaking bonds require energy = Endothermic process

27
Q

What is activation energy

A

Energy required to break bonds so chemical reaction can start

28
Q

What are energy profile diagrams

A

Show potential energy changes during course of chemical reaction

29
Q

How should energy profile diagrams in exothermic reactions look

A

Enthalpy of products < Enthalpy of reactants

Overall energy is released

30
Q

How should energy profile diagrams in exothermic reactions look

A

Enthalpy of products > Enthalpy of reactants

Overall energy is absorbed

31
Q

What are thermochemical equations

A

Sign and numerical value for energy change in equations

Enthalpy change value for reaction quoted, accompanied by equation

  • Indicates amount, per mole, of energy released / absorbed
32
Q

What are exothermic reactions thermochemical equations

A

Enthalpy change negative

Enthalpy change treated as reactant if written in equation

33
Q

What are endothermic reactions thermochemical equations

A

Enthalpy change positve

Enthalpy change treated as product if written in equation

34
Q

What is the principle of energy changes per mole in thermochemical equations

A

Comparing enthalpy change, comparsions made “per mole” of reactants

Chemical equation re-written
- “Focus” reactant coefficient of 1

35
Q

What is the effect on enthalpy change when reversing chemical reaction

A

Changes sign, not magnitude of enthalpy change

Demonstrates law of conservation of energy, true for all reversible reactions

Chemistry ATAR (3 decks)

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