(PMT) Amount of substance Flashcards

1
Q

What is the symbol for amount

of substance?

A

n

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2
Q

What is the unit used to
measure amount of
substance?

A

Mole

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3
Q

What does the Avogadro

constant represent?

A

The number of atoms per mole of the

carbon-12 isotope

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4
Q

How to calculate the mass of 1

mole of the element?

A

Mass of 1 mole = relative atomic mass in

grams

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5
Q

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

A

Moles (mol) = mass (g) / molar mass or Mr (g mol -1)

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6
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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7
Q

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

A

24 dm3

or 24000 cm3

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8
Q

Define molar gas volume

A

The volume per mole of gas molecules

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9
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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10
Q

How to calculate moles when

gas volume is given?

A
Moles (mol) = volume (dm3
) / 24
Or
Moles (mol) = volume (cm3
) / 24000
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11
Q

What are the ideal ways in

which gases behave? (5)

A

● They are in continuous motion
● No intermolecular forces experienced
● Exert pressure when they collide with each other or
container
● No kinetic energy is lost in the collisions
● When temperature increases, kinetic energy of gases also
increase

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12
Q

Write down the ideal gas
equation (in words and
symbols, including the units)

A
pV = nRT
Pressure (Pa) x volume (m3
) = number of
moles (mol) x gas constant (8.314 J
mol-1)x temperature (K)
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13
Q

1 atmospheric pressure is

equal to how many pascal?

A

1 atm = 101325 Pa

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14
Q

0℃ is equal to how many

kelvin?

A

273 K

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15
Q

What does concentration of a

solution mean?

A

It is the amount of solute dissolved in 1
dm3
of solvent

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16
Q

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

A

Moles (mol) = concentration (mol dm-3) x
volume (dm3
)

17
Q

What is a standard solution?

A

A solution of known concentration

18
Q

Write down the steps to

prepare a standard solution

A
  1. Weigh the solute using the weigh by difference method in a weighing boat
  2. In a beaker dissolve the solute using the solvent
  3. Pour the solution into a 250cm3 volumetric flask
  4. Rinse the beaker using the solution and add it to the flask (repeat 10x adding in all the washings)
  5. Add solvent to the flask carefully until bottom of the meniscus is on the calibration mark
  6. Mix the solution thoroughly to ensure complete mixing (invert 10x with a lid on)
19
Q

What do the terms
concentrated and dilute
mean?

A
Concentrated - large amount of solute per dm3
 of
solvent
Dilute - small amount of solute per dm3
 of solvent
20
Q

What is a species in a

chemical reaction?

A

Any particle that takes part in a reaction

21
Q

What are the four common

state symbols?

A
  1. Solid (s)
  2. Liquid (l)
  3. Gaseous (g)
  4. Aqueous (aq)
22
Q

What does the percentage

yield mean?

A

The efficiency of which reactants are

converted into products.

23
Q

What are the reasons for not

obtaining 100% yield? (5)

A

● Reaction may be at equilibrium (reversible)
● The reactants may be impure
● Side reactions could happen
● Reactants or products may be left behind while
transferring
● Loss of products during separation and purification

24
Q

How is percentage yield

calculated?

A

Percentage yield = (actual amount of
product (mol or g) / theoretical amount of
product (mol or g)) x 100

25
Q

What does atom economy tell

us about?

A

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

26
Q

How is atom economy

calculated?

A

Atom economy = (molecular mass of
desired product / sum of the molecular
masses of all products) x 100
(Mr= including multipliers)

27
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

28
Q

Which type of reaction has

100% atom economy?

A
Addition reactions (two or more reactants
are combined to form a single product)