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Chemistry > Topic 1 > Flashcards

Topic 1 Flashcards

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1
Q

Formula for pressure? Give units for each of the 5 values

A

PV = nRT

Pressure - pascals
n = moles
R = 8.31 Joules per kelvin mole (J k^-1 mol^-1)
V = m^3
T = kelvin
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2
Q

Describe relationship between pressure, temperature and volume

A

Volume is INVERSELY proportional to pressure
temperature is directly proportional to volume
temp is DP to pressure
V is directly proportional to 1/P and vice versa

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3
Q

Trick for limiting reactant?

A

If asked to find limiting reactant, calculate actual number of moles of each reactant, then divide by coefficient to find the limiting reactant based on which one is smaller. but REMEMBER: when asked to find the yield of one of the products you use the ACTUAL number of moles and do the ratio thing with that, not with the divided coefficient values.

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4
Q

How do you convert from cm3 to m3 for the pressure equation?

A

cm3 -> m3: divide number by 10^6

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5
Q

What is the standard temperature and pressure? (STP)

A

Temp - 273 kelvin

Pressure - 1 x 10^5 pascals

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6
Q

Equation for molar volume of a gas?

A

Molar volume = moles x 22.7

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7
Q

What does the 22.7dm3 represent?

A

At STP, 1 mole of any gas occupies 22.7 dm^3 volume

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8
Q

How to determine molar mass of a gas experimentally?

A

To collect the gas, a measuring cylinder is inverted and filled with water

measuring cylinder filled with known volume of gas from a cigarette lighter

mass of lighter recorded before and after

find change in mass in lighter

Find volume collected - convert to m3

convert temp to kelvin

R = 8.31 J k-1 mol-1

P = atmospheric pressure of water - vapour pressure

substitute these into M = mRT/PV

find molar mass VOILAAAA

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9
Q

How to calculate percentage area of the molar mass method?

A

Experimental - theoretical/theoretical x 100

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10
Q

Why is the experimental value less than the theoretical value for molar mass?

A

Lighter not dried completely before weighing
Liquid may be a mixture of propane and butane
Pressure of gas not equalised with pressure of room

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11
Q

Assumptions of the ideal gas law? (PV=nRT)

A

Particles are in constant, straight line, random motion

Collisions between particles are elastic with no loss in kinetic energy

No intermolecular forces acting between particles

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12
Q

Under what two conditions do ideal gases deviate the most?

A

High pressure
low temperature
Under these conditions, product of PV/RT is no longer equal to 1

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13
Q

Describe the ideal gas deviation curve

A

A low temperature and a high pressure cause the most deviation

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14
Q

Ideal gases have virtually no what?

A

volume
intermolecular forces

however, at high pressures, space between particles is reduced and volume of real gases cannot be negligible

real gases deviate most from ideal gas behaviour under HIGH PRESSURE and LOW TEMP

  • intermolecular forces have an effect on the pressure of a real gas compared to an ideal gas
  • IMF reduces collisions with walls of container
  • pressure exerted decreases so observed pressure is less for a real gas than ideal gas
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15
Q

Definition of an element

A

A substance that cannot be broken down by chemical means into simpler substances

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16
Q

Definition of a compound

A

2 or more elements chemically bonded together

17
Q

Definition of a mixture

A

A mixture contains more than one element and/or compound not chemically bonded together and so retain their individual properties. Their composition is not fixed

18
Q

Homogenous mixtures + example?

A

Have uniform properties and composition e.g: air, brine, amalgum.

19
Q

Heterogenous mixtures + example?

A

Have non-uniform composition and properties. e.g: salt and sand, oil and water. Properties not the same throughout. Can be separated

20
Q

Describe the difference in property of components of these mixtures and the technique used to separate them:

i) Sand and salt
ii) Hydrocarbons in crude oil
iii) iron and sulfur
iv) pigments in food colouring
v) Different amino acids

A

i) Solubility in water, solution and filtration
ii) Boiling point, fractional distillation
iii) magnetism, response to a magnet
iv) absorption to solid phase, chromatog
v) net charge at fixed pH, gel electrophoresis

21
Q

Describe the composition of a solid

A

Particles closely packed together

Inter-particle forces strong

Particles vibrate in position

They have a fixed shape, cannot flow

Fixed volume

22
Q

Describe the composition of a liquid

A

Particles more spaced

Weaker inter-particle forces

Particles can slide over each other

No fixed shape

Fixed volume

23
Q

Describe the composition of a gas

A

Particles spread out

Inter-particle forces are negligible

Particles move freely

No fixed shape

No fixed volume

24
Q

Describe the kinetic theory of matter

A

It describes that the average kinetic energy of the particles is directly proportional to the temperature of the system. The state of matter at a given temperature and pressure is determined by the strength of forces that may exist between the particles, known as inter-particle forces.

25
Q

Fluids are solids, liquids or gases?

A

Liquids and gases - basically any substance that can flow and take the shape of their container.

26
Q

What is sublimation?

A

Solid to gas

27
Q

What is condensation

A

Gas to a liquid

28
Q

Liquid to a gas?

A

Evaporation

29
Q

Gas to solid?

A

Deposition

30
Q

Liquid to solid?

A

Freezing

31
Q

Gas to a liquid

A

Condensation

32
Q

Difference between evaporation and boiling?

A

Evaporation involves the change of a liquid to a gas but unlike boiling, evaporation occurs only at the surface and takes place at temperatures below the surface. Boiling on the other hand is when particles leave throughout the body of the liquid which is why the bubbles occur. Boiling occurs at a specific temperature, determined by when the vapour pressure reaches the external pressure.

33
Q

Describe the energy input and temperature graph

A

i) As the solid is heated, the vibrational energy of its particles increases and so the temperature increases
ii) This is the melting point. Vibrations are sufficiently energetic for the molecules to move away from their fixed positions and form a liquid. Energy added during this stage is used to break the inter-particle forces and NOT to raise the kinetic energy. Temperature stays constant
iii) As the liquid is heated, the particles gain kinetic energy and so the temperature increases
iv) This is the boiling point. Now there is sufficient energy to break all of the inter-particle forces and form a gas.
v) As the gas is heated under pressure, the kinetic energy of its particles continues to rise and so does temperature

PRESSURE REMAINS CONSTANT

34
Q

Describe the problems with the butane molar mass experiment

A

Butane can dissolve in the water, causing the Mr value to raise. Use colder water in which it is less soluble

Some air/water vapour can be collected with the gas, decreasing the Mr, use chilled boiled water to ensure less air is present

Butane gas escapes as the cylinder was tilted, causing molar mass to be greater because the decrease in mass of the lighter would be exaggerated.

35
Q

What could cause the Molar Mass of butane to be lower than expected

A

If pressure and volume are high.

36
Q

Describe the relationship between density and temperature

A

inversely proportional

37
Q

Does doubling temperature from 25 degrees to 50 degrees celcius change volume of a gas?

A

No, because when temperature is converted to kelvin, it is actually not doubled so volume does not double

Chemistry (7 decks)

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