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Calculations Flashcards

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1
Q

What is the relative atomic mass also known as?

A

Ar

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2
Q

What does relative atomic mass represent?

A

The weighted average mass of an atom, taking into account the abundance of all the isotopes of that element.

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3
Q

How is relative atomic mass calculated?

A

Relative atomic mass = (mass of 1st isotope x abundance) + (mass of 2nd isotope x abundance) / Total abundance of isotopes

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4
Q

What is another name for relative formula mass?

A

Mr

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5
Q

How is relative formula mass calculated?

A

Relative formula mass = sum of all the Ars (listed on periodic table) of the atoms in the formula.

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6
Q

What is the relationship between total Mrs on both sides of a chemical equation?

A

Total Mrs on both sides of the equation are the same.

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7
Q

What does percentage composition of an element in a formula allow us to determine?

A

How much of a certain element is present in a formula unit by mass.

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8
Q

How is the percentage composition of an element in a compound calculated?

A

Percentage composition = (Sum of the A of a particular element / M of compound) x 100%

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9
Q

What is the definition of one mole?

A

One mole is the amount of substance which contains 6.02 x 10^23 particles.

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10
Q

How do you calculate moles?

A

Moles = Mass in grams / Mr

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11
Q

What is the mass in grams of one mole of atoms or molecules equal to?

A

The relative formula mass (Ar or Mr).

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12
Q

What can be calculated from balanced symbol equations?

A

The masses of reactants and products.

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13
Q

What do the balancing numbers in a chemical equation represent?

A

The ratios of moles of the substances.

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14
Q

What is the first step in reacting masses calculations?

A

Use the given mass of the substance and its M to work out its moles.

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15
Q

How do you determine the moles of other substances in a reaction?

A

Using the mole ratio / balancing numbers.

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16
Q

What is necessary to work out the mass in grams of other substances?

A

Using their Mr.

17
Q

What can be determined if the masses of the reactants and products are known?

A

The chemical equation with balancing numbers.

18
Q

What is the first step to balance an equation using moles?

A

Calculate the moles of each substance using the mass and Mr.

19
Q

How do you write the ratios for balancing the equation?

A

Write these in a ratio.

20
Q

What should you do to get whole number ratios?

A

Divide all the numbers in the ratio by the smallest number.

21
Q

True or False: Total relative formula mass is always conserved in a chemical reaction.

A

True

22
Q

What is the empirical formula?

A

The simplest whole number ratio of the elements in a compound

It is determined by calculating the moles of each element and dividing by the smallest number of moles.

23
Q

How can you determine the empirical formula from a mole ratio?

A

Divide the mole ratio by the smallest number

For example, magnesium chloride has a mole ratio of 1:2, resulting in the formula MgCl.

24
Q

What is the volume occupied by 1 mole of any gas at room temperature and pressure?

A

24 dm³ or 24,000 cm³

This is a standard volume for gases under these conditions.

25
Q

How do you calculate gas volume in dm³?

A

Gas volume (dm³) = moles x 24 dm³

This formula is used for calculating the volume occupied by a given number of moles of gas.

26
Q

What is the formula to calculate percentage yield?

A

Percentage yield = (actual yield / theoretical yield) x 100%

This calculation helps to evaluate the efficiency of a chemical reaction.

27
Q

What factors can prevent achieving 100% yield in practice?

A

Side reactions, incomplete reactions, transfer losses

These factors can lead to discrepancies between actual and theoretical yields.

28
Q

What is atom economy?

A

Atom economy = (sum of Mₘ of useful products / sum of Mₘ of all reactants) x 100%

It measures the efficiency of a reaction in terms of the amount of useful products generated.

29
Q

When does a reaction have 100% atom economy?

A

When there is only one product

This indicates that all reactants are converted into the desired product without waste.

30
Q

Why is higher atom economy beneficial?

A

It leads to better profits and sustainability by using fewer natural resources and creating less waste

More product made means more money can be made from the same raw materials.

31
Q

What is a limiting reactant?

A

The reactant in a chemical reaction that is completely consumed first

It determines the amount of product formed in the reaction.

32
Q

True or False: Equal numbers of moles of any gas occupy different volumes at room temperature and pressure.

A

False

Equal moles of gases occupy the same volume under these conditions.

33
Q

What is the reactant that is completely used up in a chemical reaction called?

A

Limiting reactant

The limiting reactant limits any further products being made when it is used up.

34
Q

What is the term for the reactant that is not fully used up in a chemical reaction?

A

Reactant in excess

This reactant remains after the reaction has completed.

35
Q

What are the steps to determine the limiting reactant?

A
  1. Work out how many moles there are of each reactant.
  2. Consider the balancing numbers to identify the limiting reactant.
36
Q

To calculate the amount of product formed in a reaction, which reactant’s moles should be used?

A

Moles of the limiting reactant

The amount of product depends on the limiting reactant.

37
Q

Fill in the blank: The limiting reactant is important because it _______ any further products being made.

A

limits

38
Q

True or False: The reactant in excess is used up completely during the reaction.

A

False

The reactant in excess is not fully used up.

Chemistry (16 decks)

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