Amount Of Substance Flashcards

1
Q

Define relative atomic mass

A

The Weighted average mass of an atom of an element taking into account its naturally occurring isotopes relative to 1/12 th the mass of an atom of carbon 12

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2
Q

Define relative molecular mass

A

The mass of a molecule compared to the 1/12 the relative atomic mass of an atom of carbon 12

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3
Q

What is relative formula mass?

A

Similar to Mr however this is used for ionic compounds as they do not exist as molecules.

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4
Q

What is a mole?

A

The amount of substance that contains the same number of atoms as 12g of carbon 12

Avagadros constant:

6.02x10^23

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5
Q

What’s is empirical formula?

A

The simplest whole number ratio of atoms in each element present in a compound

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6
Q

What is stoichiometry?

A

The quantitative relationship between reactants and products in a balanced equation.

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7
Q

What equations do we use to find moles?

A

Moles = mass / Mr

Moles = volume x concentration / 1000

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8
Q

What is the ideal gas equation?

A

PV=nRT

P-pressure
V-volume
n-number of moles
R-gas constant (8.314)
T-temperature
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9
Q

What key assumptions are made when using the gas constant?

A

Any intermolecular forced between the gas molecules is negligible

Relative to the volume of their container the volume occupied by the molecules themselves is negligible.

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10
Q

How do you find the empirical formula?

A
  1. Find the masses of each of the elements present in a compound
  2. Work out the number of moles of atoms of each element
  3. Convert the number of moles of each element into a whole number ratio.
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11
Q

What is the molecular formula?

A

The actual number of atoms of each element in a molecule or compound.

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12
Q

What is the equation for atom economy?

A

Atom economy= mass if desired product / total mass of reactants

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13
Q

What is the equation for percentage yield?

A

% yield= actual yield / theoretical yield

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14
Q

What may cause the percentage yield to not be 100%?

A

Some reactant may remain unreacted

Some reactant may be lost

The reaction may not have gone to completion.

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15
Q

How do you calculate percentage uncertainty

A

% uncertainty = absolute uncertainty / measured value x100

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