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HL Chem > 1. stoichemetric relationships! > Flashcards

1. stoichemetric relationships! Flashcards

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1
Q

what is a homogenous mixture

A

uniform composition AND properties

heterogenous do NOT

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2
Q

given differing boiling points in a mixture, how would they be seperated?

A

fractional distillation

eg air

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3
Q

how to determine ionic equation

A
  1. write full chem eqn
  2. break down compounds into ions
  3. cancel repeated ions on each side
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4
Q

boiling vs evaporation?

A

boiling at specific temp – vapour pressure reaches external atmospheric pressure

evaporation only at surface + at temps BELOW boiling point

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5
Q

when given a graph of state change hwo to explain the flat parts (no change in temp)

A

no increase in kinetic energy or temp bc ALL THE ENERGY GOES INTO BREAKING BONDS

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6
Q

define the avogadro constant!

A

the number of particles equivalent to the RELATIVE ATOMIC MASS / MOLECULAR MASS of a substance in grams

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7
Q

what is the value of the avogardo constant

A

6.02 x 10^23 g/mol

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8
Q

what is avogadros constant used for

A

number of atoms / particles

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9
Q

define molar mass

A

one mole of a substance = same number of atoms in 12g of 12C

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10
Q

define relative atomic mass

A

weighted average mass of one atom compared to one twelfth of the mass of a carbon-12 atom

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11
Q

define relative isotopic mass

A

mass of a particular atom of an isotope compared to 1/12th the mass of a 12C atom

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12
Q

define isotopes

A

atoms of the same element with different number of neutrons

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13
Q

define relative atomic mass

A

weighted average mass of a molecule compared to 1/12th the mass of a 12C atom

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14
Q

define empirical formula

A

the simplest whole number ratio of the atoms of each element present in one molecule/formula unit of the compound

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15
Q

define percentage yield

A

how much of a particular product you get from reactants compared to max theoretical amt

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16
Q

actual vs theoretical yield

A

actual: mol/mass obtained experimentally

theoretical: mol/mass obtained thru mass creation

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17
Q

what is avogardos law used for

A

determining mole ratio of reacting gases to be determined from volumes of the gases

18
Q

what is avogardos law

A

equal volumes of gases must contain the same number of molecules

(At standard temp and pressure. 1 mol)

19
Q

value for avogardos law

A

standard temp + pressure

1 mole of gas = vol of 22.7dm3

20
Q

conditions of STP (standard temp and pressure)

A

0C / 273K
100kPa

21
Q

define the kinetic theory of gases

A

states that molecules in gases are constantly moving

22
Q

5 assumptions of the kinetic theory of gases

A
  1. gas molecules move very fast and randomly
  2. molecules hardly have any volume
  3. no intermolecular forces = gas molecules do not attract or repel each other
  4. elastic collisions: no kinetic energy lost when gas molecules collide
  5. temperature of gas directly proportional to average kinetic energy of molecules
23
Q

volume of a gas depends on 2

A

temperature

pressure

24
Q

ideal gas equation

A

PV = nRT

pressure x volume = moles x gas constant (8.31) x temp

25
Q

what is the gas constant?

A

8.31 J/K/mol

26
Q

what unit is volume in in the ideal gas equation

A

m3

(1 m3 = 1000dm3)

27
Q

what unit is pressure in the ideal gas equation

A

Pa

1 kPa = 1000 Pa

28
Q

what unit is temperature in the ideal gas equation

A

K

C + 273 = K

29
Q

conversion from m3 to cm3

A

multiply by 10^6

vice versa

30
Q

what is Boyle’s law

A

(in gases) pressure is invesely proportional to the volume (at a constant temperature)

PV is a constant

31
Q

pressure against volume graph gives? vs pressure against 1/vol

A

curved inwards, down (like and L)

gives a straight directly increasing line

32
Q

at what conditions do real gases deviate from ideal gas equation 2 + why?

A

high pressures
low temperatures

assumes tiny volume of molecules vs container BUT at these conditions = closer tgt = takes up larger vol of space

pressure less than expected bc itnernolecular forces exist when molc close tgt

33
Q

what is a standard solution

A

concentrations known precisely

(use volumetric flask!)

34
Q

what is the concentration of a solution?

A

amount of solute dissolved in a solvent to make 1dm3 of solution

35
Q

cm3 to dm3

A

divide by 1000

36
Q

define ppm

A

parts per million

mass of 1 mg dissolved in 1 dm3 of water (or 1kg of water)

37
Q

1 dm3 = how many litres ?

A

1 litre / kg

38
Q

parts (in ppm) to kg

A

parts is in mg

x 10^-6 (aka 1 mil)

39
Q

charge of CO3 ion?

A

2-

40
Q

uncertainty of burette

A

+- 0.05

HL Chem (28 decks)

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