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Chemistry - S1 > Quantitative Chemistry > Flashcards

Quantitative Chemistry Flashcards

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1
Q

What is the Relative Atomic Mass and its symbol?

A

The Ar of an element is a weighted mean mass of the isotopes of an element compared with that of the C (12) Isotope, which has a mass of exactly 12.

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2
Q

What is the Relative Molecular Mass and its symbol

A

The Mr of a substance is the sum of the masses of all the atoms present in the formula of that element or compound. It is used when calculating the mass of a covalent compound.

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3
Q

What is the relative Formula Mass and its symbol

A

The Mr of a substance is the sum of the masses of all the atoms present in the formula of that element or compound. It is used when calculating the mass of a ionic compound.

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4
Q

How to calculate the percentage of an element in a compound?

A

% of an element = Total mass of element in the compound/ Mr X 100

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5
Q

Calculate the percentage by mass of oxygen in MgSO4

A

First calculate the Mr: 24 + 32 + (4x16) = 120

There are four oxygen atoms so the mass of the oxygen is 4x16 = 64 So:

% of O in MgSO4 = 64/120 x100

= 53.3% (You don’t need to memorise this its just an example)

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6
Q

What is the mole?

A

The relative formula mass of a substance in grams

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7
Q

How many particles is in one mole of a substance?

A

One mole of a substance is 6.02 X 10 (to the power of 23)

It is obtained by weighing out RAM or FRM in grams

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8
Q

What is the equation to find the mole of a substance?

A

Moles = Mass of substance/Ar or Mr

Mass of substance must be in grams
Ar for elements
Mr for compounds

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9
Q

What is the equation to find the Mass of a substance?

A

Mass = mole x Ar or Mr

Mass of substance must be in grams
Ar for elements
Mr for compounds

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10
Q

How to use ratios to interpret quantitive equations

A

Too annoying to explain look in book idiot

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11
Q

Why can we interpret chemical reactions quantitatively?

A

As no atoms are made or lost

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12
Q

What is the percentage yield of a chemical reaction?

A

Percentage yield of a chemical reaction shows how much product was actually made compared with the amount of product that was expected.

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13
Q

What is the equation to find the percentage yield?

A

percentage yield =

Actual yield of desired product / Theoretical yield of desired product X 100

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14
Q

Why is the percentage of a product less than 100%

A
  • Loss of product in separation from the reaction mixture
  • Side reactions
  • Reaction may be reversible and not go to completion
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15
Q

What is water of crystallisation

A

Water that is chemically bonded into the crystal structure

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16
Q

What does Hydrated mean?

A

Solid crystals contains water of crystallisation

17
Q

What does dehydration mean?

A

Means removal of water of crystallisation

18
Q

What is an anhydrous substance?

A

The substance does not contain water of crystallisation

19
Q

What is the degree of Hydration?

A

The number of moles of water of crystallisation chemically bonded in 1 mole of the compound.

20
Q

What is the empirical formula?

A

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

21
Q

What is the molecular formula?

A

The actual number of atoms of each element in a molecule

22
Q

How do you calculate the percentage of water of crystallisation in a compound?

A

% water of crystallisation =

degree of hydration X Mr of water / Mr of the compound X 100

23
Q

What is the method to find the % of water of crystallisation in magnesium sulfate crystals?

A
  1. Place a small amount of the magnesium sulfate crystals in a boiling tube. Place a dry piece of cobalt chloride paper at the neck of the boiling tube. Heat the crystals and record observations
  2. Record the mass of a crucible

3.Weigh out about 5g of the magnesium sulfate crystals

  1. Heat the crystals for 5 minutes. Now reweigh using filter paper on the balance.
  2. Continue to heat the salt for a further 5 minutes until you get a constant mass.
  3. Draw a diagram of the apparatus
  4. Work out the % of water of crystallisation
  5. Work out the theoretical % of water of crystallisation if the formula is MgSO4.7H20
24
Q

What is thermal decomposition?

A

The breakdown of a solid using heat and can be completed to completion by heating to a constant mass

Chemistry - S1 (8 decks)

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