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Chemistry HL IB 2020-22 > 1. Stoichiometric Relationships > Flashcards

1. Stoichiometric Relationships Flashcards

1
Q

What is kinetic energy?

A

Energy related to motion of an object

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2
Q

Solid, liquid, gas: Arrangement

A

Solid: Closely packed
Liquid: Also close together but less then solid
Gas: Most spread out, far apart

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3
Q

Solid, liquid, gas: Intermolecular forces

A

Solid: Strongest forces
Liquid: Weaker forces
Gas: Negligible forces

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4
Q

Solid, liquid, gas: Motion

A

Solid: Vibrate at fixed positions
Liquid: Slide past each other
Gases: Move randomly

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5
Q

Solid, liquid, gas: Shape

A

Solid: Fixed shape
Liquid: No fixed shape, takes shape of container
Gas: No fixed shape

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6
Q

Solid, liquid, gas: Volume

A

Solid: Fixed volume
Liquid: Fixed volume
Gas: No fixed volume

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7
Q

What are all the changes of state?

A
  • Solid to liquid: Melting
  • Liquid to gas: Evaporation
  • Gas to liquid: Condensation
  • Liquid to solid: Freezing
  • Solid to gas: Sublimation
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8
Q

What is opposite of sublimation?

A

Deposition (gas to solid)

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9
Q

Why does change of state occur?

A

An increase in temperature = increase in average kinetic energy of molecules which allows them to overcome intermolecular forces and hence build or break bonds

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10
Q

Examples of sublimation

A

Iodine, CO2, NHCl, Mothballs, Dry ice

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11
Q

Difference between evaporation and boiling

A
  • Evaporation takes place at surface and below boiling point, happens at range of temperatures
  • Boiling has a specific temperature and occurs throughout the liquid
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12
Q

What does flat part on heating or cooling curve show and why?

A

It shows the melting or boiling points because when there is a change of state, the temperature remains constant

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13
Q

Density

A

Mass per unit volume (D= m/v)

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14
Q

Unit for density

A

g/cm^3 or kg/m^3

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15
Q

Element

A

Something that is made of the same kind of atom

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16
Q

Compound

A

Chemically combined substance of 2 or more different elements

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17
Q

Are H2 and O2 compounds?

A

No. They are molecules

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18
Q

Differences between elements and compounds

A
  • Elements are made of one type of atom
  • Elements cannot be further broken down while compounds can be chemically
  • Elements are represented by a symbol instead of formulae
  • Element’s properties are determined by valence electrons while compound’s properties differ from their constituent elements
  • 118 known elements while compounds have endless possibilities
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19
Q

Mixture

A

2 or more substances that are not chemically combined

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20
Q

Difference between mixtures and compounds

A
  • Compounds are chemically combined while mixtures are physically
  • Compounds are in fixed ratio
  • Compounds are pure
  • Compounds have a formulae
  • Properties of compounds differ but mixtures retain properties of their elements/substances
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21
Q

Difference between homogenous and heterogenous mixture

A
  • Homogenous have uniform dispersion
  • Homogenous have fixed ratio/composition
  • Heterogenous are immiscible while homogenous do not physically separate on standing
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22
Q

Examples of homo and heterogenous mixtures

A

Homogenous: Air, honey
Heterogenous: Sand + water, oil + water

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23
Q

Are solutions homo or heterogenous?

A

Homogenous

24
Q

Solute

A

Substance that is DISSOLVED

25
Q

Solvent

A

Substance that DISSOLVES

26
Q

Concentration

A

Amount of solute dissolved per unit volume of solution

27
Q

Unit of concentration

A

g/dm^3 or mol/dm^3

28
Q

Relative atomic mass

A

Weighted average mass of an atom compared to 1/12 mass of an atom of Carbon-12

29
Q

Unit of molar mass

A

g/mol

30
Q

Avogadro’s constant

A

6.02 x 10^23

31
Q

What is molar mass?

A

Mass of one mole of a substance

32
Q

How do you calculate number of moles?

A

Total mass/ Molar mass

33
Q

Calculating mass of one molecule

A

Molar mass/ Avogadro constant

34
Q

How do you find empirical formula?

A

Divide percentage by mass of element present in a mole. Find simplest whole number ratio

35
Q

What is percentage composition?

A

Mass of element in a compound/ Molar mass of compound

36
Q

How to find molecular formulae?

A

Divide mass by molar mass of empirical formula and multiply that into the empirical compound

37
Q

What are limiting and excess reagents?

A

Limiting: Limit amount of product made in a chemical reaction
Excess: Reactant that remains at the end of the reaction

38
Q

How do you find excess reagent?

A

Convert elements from mass in grams to amount in mole. Divide each amount by coefficient in balanced equation. The higher value is the one in excess

39
Q

What is theoretical yield?

A

Maximum amount of product that can be produced assuming all reactant has reacted

40
Q

How do you calculate percentage yield?

A

(Actual/Theoretical yield) *100

41
Q

What is Avogadro’s law?

A

States that equal volume of gas at same temp. and pressure contain equal number of particles

42
Q

What is kinetic molecular theory of gases? 5 postulates.

A
  • Particles are in constant, random straight line motion
  • Negligible forces of attraction between particles
  • Collisions between particles or with surface are elastic (no energy lost)
  • Distance between particles > size of particles so negligible volumes
  • Kinetic energy is proportional to temperature
43
Q

What is molar volume?

A

Volume occupied by 1 mole of gas at STP. It is 22.7 dm^3

44
Q

Boyle’s Law

A

PV=k or pressure is indirectly proportional to volume

45
Q

How do you convert Kelvin to Celsius?

A

K is Celsius + 273

46
Q

Charles’ Law

A

Volume is proportional to temperature

47
Q

What is the general gas equation?

A

P1V1/T1= P2V2/T2. Units can be any as long as they are the same

48
Q

Ideal gas equation

A 
PV= nRT where:
P= Pa
V= m^3
n= mol
R= 8.31 J/Kmol 
T= K
49
Q

What are the conditions of a real gas?

A

Occurs at high pressure and low temp.

50
Q

Why is there greatest deviation from ideal gas in a real gas?

A

Because at low temp, they move slower and at high pressure, they are more narrowly spaced

51
Q

Why are gases like helium more ideal than real?

A

They have low molar mass and weakest intermolecular forces

52
Q

Why do NH3 and CO2 deviate greatly?

A

NH3 has strong H bonds while CO2 has very strong forces

53
Q

Under what conditions do gases behave more like an ideal gas?

A

At high temperature and lower pressure. They exhibit the 5 postulates of kinetic theory

54
Q

How do you calculate concentration?

A

Concentration= Amount of solute (mol)/volume of solution (dm^3)
OR n= CV

55
Q

How do you calculate concentration for very dilute solutions?

A

It’s C= n/V * 10^6. Calculated in ppm (parts per million). Note: 1ppm means 1dm^3 solution has 1 mg of solute

56
Q

What are standard solutions?

A

Solutions with precisely known concentrations

  • High purity
  • High molar mass
  • Low reactivity
57
Q

How would you calculate back titrations for finding CaCO3 in eggshells through HCl?

A
  1. Excess HCl is reacted with aq. NaOH
  2. Subtract acid reacted with NaOH from total acid reacted with egg shell to find mole of acid that reacted
  3. Calculate mass of CaCO3 by moles
  4. Divide mass of CaCO3 by total mass of eggshell
  5. Find percentage

Chemistry HL IB 2020-22 (19 decks)

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