C3 Quantitative Chemistry

Question 1

How do you find the relative formula mass of a compound?

Answer 1

• Add the relative atomic masses of the atoms in the compound.

Question 2

How do you find the percentage mass of an element in a compound?

Answer 2

( (Atomic mass of element x number of atoms of that element) / Relative formula mass of the compound ) x 100

Question 3

What is the mole of any substance?

Answer 3

• It is the amount of that substance that contains an Avogadro number of particles. The particles could be atoms, molecules, ions or electrons.

Question 4

What is the value of Avogadro’s constant?

Answer 4

• 6.02 x 10²³

Question 5

What is one mole of atoms or molecules of any substance’s mass equal to?

Answer 5

• It is the equal to the relative formula mass of that substance.

Question 6

What is the formula for number of moles?

Answer 6

Moles = mass / relative formula mass

Question 7

In a chemical reaction mass is always blank

Answer 7

Conserved

Question 8

How can we show that mass is conserved in a reaction?

Answer 8

• Add the relative formula masses on each side of the reaction, these will be equal.

Question 9

What is the explanation for the mass increasing in an unsealed reaction vessel after a reaction?

Answer 9

• This is due to one of the reactants being a substance that is found in the air.
• The gas in the air such as oxygen reacts with one of the reactants causing an increase in mass of the products.
• Such as metal and oxygen making a metal oxide.

Question 10

What is the explanation for the mass decreasing in an unsealed reaction vessel after a reaction?

Answer 10

• If one of the products is a gas then it will dissipate into the surroundings.
• Such as a metal carbonate making a metal oxide and carbon dioxide
• Mass will be lost as the weight from the carbon dioxide with dissipate into the surroundings.

Question 11

Give the process to Balance Equations using Reacting Masses.

Answer 11

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