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Physical Chemistry > Section 1.2 - amount of substance > Flashcards

Section 1.2 - amount of substance Flashcards

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1
Q

Relative atomic mass

A

-mean average mass of all atoms of an element (taking isotopes into account) relative to 1/12 mass of an atom of carbon 12
-Ar

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2
Q

Relative molecular mass

A

-mean average mass of a molecule relative to 1/12 mass of an atom of carbon 12
-Mr

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3
Q

Relative formula mass

A

-used for ionic compounds as they don’t exist as molecules
also represented by Mr symbol

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4
Q

what is the symbol for amount of substance?

A

n

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5
Q

what is the unit used to measure amount of substance?

A

moles

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6
Q

what does the Avogadro constant represent?

A

the number of atoms per mole of the carbon 12 isotope

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7
Q

how to calculate the mass of one mole of the element

A

mass of one mole = relative atomic mass in grams

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8
Q

how to calculate moles when mass and molar mass are given?

A

moles (mol) = mass(g) / molar mass (g mol -1)

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9
Q

what is a mole?

A

-amount of substance that contains 6.022 * 10^23 particles
-Ar of an element has one mole of atoms

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10
Q

how to work out moles when given number of particles

A

moles = number of particles / Avogadro’s constant

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11
Q

state Avogadro’s law

A

under the same temperature and pressure, one mole of any gas would occupy the same volume

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12
Q

what factors affect the volume of a gas?

A

-number of moles of a gas
-pressure applied to the gas
temperature of the gas
volume doesn’t depend on the type of gas

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13
Q

how much volume does a gas occupy, at room temperature and pressure?

A

24 dm^3 or 24000cm^3
(molar volume)

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14
Q

conversion from dm^3 to cm^3

A

*1000

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15
Q

define molar gas volume

A

the volume per mole of gas molecules

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16
Q

why do different gas particles occupy the same volume?

A

the gas particles are very spread out, hence individual differences has no effect

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17
Q

how to calculate moles when gas volume is given

A

moles (mol) = volume (dm^3) / 24
or
moles (mol) = volume (cm^3) /24000

18
Q

What area the ideal ways in which gases behave?

A

-they are in continuous motion
-no intermolecular forces experienced
-exert pressure when they collide with each other or the container
-no kinetic energy is lost in the collisions
-when temperature increases, kinetic energy of gases also increase

19
Q

How to convert from kPa to Pa

A

*1000

19
Q

ideal gas equation

A

pV = nRT
p = pressure (Pa)
v = volume (m^3)
n = number of moles
t = temperature (Kelvin-K)
R = universal gas constant (8.31 J mol^-1 K^-1

20
Q

How to convert from dm^3 to m^3

A

/1000 (10^3)

21
Q

How to convert from cm^3 to m^3

A

/1000000 (10^6)

22
Q

How to convert from degrees Celsius to Kelvin

A

+273

23
Q

What is room temperature and pressure?

A

-temperature = 298K
-pressure = 101kPa

24
Q

What is standard temperature and pressure?

A

-temperature = 237K
-pressure = 100kPa

25
Q

how many pascals is 1 atmospheric pressure equal to?

A

1 atm = 101325 Pa

26
Q

0 degress celsius is equal to how many Kelvin?

A

273K

27
Q

What does concentration of a solution mean?

A

it is the amount of solute dissolved in 1 dm^3 of solvent

28
Q

how do you calculate moles when volume and concentration are given?

A

moles (mol) = concentration (mol dm^-3) * volume (dm^3)

29
Q

what is a standard solution?

A

a solution of known concentration

30
Q

how do you prepare a standard solution?

A

-weigh the solute using the weigh by difference method
-in a beaker dissolve the solute using the solvent
-pour the solution into a volumetric flask
-rinse the beaker using the solution and add it to the flask
-add solvent to the flask carefully until it reaches the graduation line
-mix the solution thoroughly to ensure complete mixing

31
Q

what does the term concentrated mean?

A

large amount of solute per dm^3 of solvent

32
Q

what does the term dilute mean?

A

small amount of solute per dm^3 of solvent

33
Q

what is a species in a chemical reaction?

A

any particle that takes part in a reaction

34
Q

what are the 4 common state symbols?

A

-(s) = solid
-(g) = gas
-(l) = liquid
-(aq) = aqueous

35
Q

why may percentage yield be less than 100?

A

-reaction may be at equilibrium
-the reactants may be impure
-other reactions may occur (side reactions)
-reaction may be incomplete
-products are lost during separation or purification
-reactants or products may be left behind while transferring

36
Q

how do you calculate percentage yield?

A

(mass of product obtained / theoretical yield) *100

37
Q

what does percentage yield mean?

A

the efficiency of which reactants are converted into products

38
Q

what does atom economy tell us about?

A

the proportion of desired products compared with all the products formed in the reaction

39
Q

how do you calculate atom economy?

A

(molecular mass of desired product / sum of the molecular masses of all products) *100

40
Q

does 100% yield mean 100% atom economy?

A

no, even if all the reactants are converted into products, not all products of the reaction will be the required products

41
Q

which type of reaction has 100% atom economy?

A

addition reactions (two or more reactants are combined to form a product)

Physical Chemistry (3 decks)

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