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Chemistry > 2.3 Amount of Substance > Flashcards

2.3 Amount of Substance Flashcards

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1
Q

What is a mole ?

A

Amount of any substance certaining as many particles as there are carbon atoms in 12g of carbon-12.

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2
Q

What is Avogadro’s constant ?

A

6.02x10^23
It is the number of atoms per mole of carbon-12.

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3
Q

What is molar mass ?

A

It is the mass per mole of a substance (g/mol-1)

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4
Q

How to work out number of moles?

A

Mass (g) / molar mass (g/molar-1)

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5
Q

How to work out number of particles ?

A

Number of moles x Avogadro’s constant

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6
Q

What does 1 mole of gas at room temperature and pressure obtain?

A

24 dm^3 (24dm^3 = 24000cm^3)

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7
Q

Molecular Formulae

A

Number of atoms of each element in a molecule.

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8
Q

Empirical Formula

A

Simplest whole number ratio of atoms of each element in a compound.

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9
Q

How to calculate empirical formula ?

A

1) Mass/molar mass = no of moles.
2) Divide by smallest number.
3) Make a whole number ratio.
4) Create formula.

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10
Q

Relative molecular mass

A

Compares mass of molecule with mass of an atom of carbon-12.

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11
Q

Relative formula mass

A

Compares mass of formula unit to that of an atom of carbon-12.

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12
Q

Why are many coloured salts hydrated ?

A

This is because water is a part of their crystalline structure. This water is known as the water of crystallisation.

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13
Q

What happens when copper (II) sulphate salt is heated ?

A

Water bonds within the crystal are broken and water is driven off leaving behind the white anhydrous powder.

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14
Q

Equation for copper (II) sulphate reaction

A

CuSO4.5H2O = CuSO4 + 5H2O

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15
Q

What happens to heated CuSO4 when no water is returned ?

A

Crystalline structure is lost and white anhydrous powder remains.

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16
Q

Equation for volume

A

Volume = number of moles x 24 dm^3

17
Q

What is the ideal gas equation ?

A

pV = nRT

P= pressure 1atm = 101000pa
V = volume 1dm = 1000cm
N = no of moles (mol)
R = molar gas constant =8.314 mol-1
T= temp(•c) +273 = kelvin

18
Q

What is concentration ?

A

Concentration is the number of moles of a solute dissolved in 1dm^3 of a solution.

19
Q

What is the equation for finding concentration?

A

concentration= Mass or Moles / Volume

20
Q

What is a standard solution?

A

A solution with a known concentration.

21
Q

What is the molar gas volume ?

A

Volume per mole of gas molecules at standard temperature and pressure.

22
Q

Equation for Molar gas volume

A

number of moles= volume/molar gas volume

23
Q

What is the stoichiometry ?

A

The ratio of number, from balanced equation, of the amount of moles of each substance.

24
Q

What is percentage yield ?

A

% of a desired product.

25
Q

What is theoretical yield ?

A

Maximum possible amount of product that can be produced.

26
Q

What is actual yield ?

A

How much product is actually produced from a reaction. Usually lower than theoretical yield.

27
Q

Equation for percentage yield

A

%=actual yield/theoretical yield x 100

28
Q

What are excess and limiting reagents ?

A

Limiting reagent is reactant not in excess that gets used up first in reaction.

29
Q

How to find limiting reagent ?

A

1) Find moles of each reactant in equation.
2)Find smallest amount of moles.
3)Use mole number to find amount of moles for other products based on stoichiometry.

30
Q

What is atom economy ?

A

Atom economy is a measure of how well the atoms have been utilised.

31
Q

Equation for atom economy

A

sum of desired amount/ sum of molar mass of all x 100

32
Q

Why are high atom economies good ?

A

Means reaction produced large quantities of desired product, with little waste products being made. More sustainable as it makes most use out of natural resources used.

Chemistry (20 decks)

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