2.3 AMOUNT OF SUBSTANCE Flashcards

1
Q

What is carbon-12?

A

Carbon-12 is the standard isotope used to base all atomic masses on

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2
Q

What is Avogadro’s constant?

A

Avogadro’s constant is the number of particles per mole of substance.
6.02x10^26

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3
Q

What is amount of substance?

A

Amount of substance is a quantity used to count the number of particles in a substance, measured in moles

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4
Q

What is molar mass?

A

Molar mass is the mass of 1 mol of substance measured in g/mol

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5
Q

What is the equation linking moles, mass and molar mass?

A

Amount of substance (mol) = mass (g) / molar mass (g)

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6
Q

What is the molecular formula?

A

The molecular formula is the number of atoms of each element in a molecule
- O2, CO2, P4

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7
Q

What is the empirical formula?

A

The empirical formula is the simplest whole number ratio of atoms or ions of each element in a compound
- Mg, C, NaCl

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8
Q

What is relative molecular mass?

A

Relative molecular mass compares the mass of a molecule with the mass of an atom of carbon-12

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9
Q

What is relative formula mass?

A

Relative formula mass compares the mass of a formula unit with the mass of an atom of carbon-12

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10
Q

What is water of crystallisation?

A

Water of crystallisation is water molecules that are bonded into a crystalline structure of a compound

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11
Q

What are hydrous and anhydrous?

A

Hydrous- contains water molecules
Anhydrous- does not contain water molecules

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12
Q

What equation links moles, concentration and volume?

A

Moles (mol) = concentration (mol/dm3) x volume (dm3)

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13
Q

What does Avogadro’s law state?

A

Avogradro’s law states that equal volumes of gases at the same temperature and pressure contain an equal number of moles

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14
Q

What equation links moles, volume and molar gas volume?

A

Moles (mol) = volume (dm3) / molar gas volume (24dm3/mol)

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15
Q

What is the ideal gas equation?

A

The ideal gas equation is:
pressure (Pa) x volume (dm3) = moles (mol) x gas constant (8.31 J/mol/K) x temperature (K)

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16
Q

What does it mean to behave like an ideal gas?

A

To be an ideal gas, gases must:
- have no forces between particles
- have a negligible size of particles

17
Q

Why do we not get 100% product yield?

A

Why we don’t get 100% product yield:
- reaction may not go to completion
- other reactions may have taken place
- purification may result in loss of product

18
Q

What is the equation for percentage yield?

A

Percentage yield = actual yield / theoretical yield x 100

19
Q

What is the limiting reagent and reagent in excess?

A

Limiting reagent and reagent in excess:
- one reactant is usually in excess (more of it than needed)
- limiting reactant will be used up and once done the reaction will stop
- limiting reactant determines how much product will form

20
Q

What is atom economy?

A

Atom economy measures how well atoms of the reactants have been put to use
- assumes 100% yield
- products of which are not desired and have to be disposed of are called waste products
- products which are not desired but can be sold or utilised elsewhere are called by-products

21
Q

What is the equation for atom economy?

A

Atom economy = molar mass(es) of desired product(s) / molar masses of all products

22
Q

Why should atom economy be improved?

A

Atom economy should be improved because:
- improves efficiency of process
- reduces waste
- preserves raw materials
- increases sustainability (meeting the needs of today without compromising the ability for future generations to meet their needs)