2- Formulas And Mass

Question 0

How do you find the number of neutrons from a periodic table?

Answer 0

Mass number - atomic number (bigger number minus smaller)

Question 1

What is the relative atomic mass?

Answer 1

The average mass number of the isotopes of an element

Question 2

How do you find the relative formula mass?

Answer 2

Add up the relative atomic masses

Question 3

How you find the relative atomic mass?

Answer 3

The number of protons and neutrons in the element (usually the mass number)

Question 4

What is one mole?

Answer 4

The same as the relative atomic mass of the element, or the same as the relative formula mass when dealing with compounds

Question 5

What is hydrogens two isotopes?

Answer 5

Deuterium (2)

Tritium (3)

Question 6

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

Answer 6

The relative atomic mass of the element
_______________________________________ X 100
The relative formula mass of the compound

Question 7

What is the empirical formulae?

Answer 7

The simplest integer ratio of the atoms or ions of each element in a compound
Eg. C2H4 can be divided by 2 into CH2 (can be done in moles or number of element)

Question 8

How to find the empirical formulae from mass or percent?

Answer 8

Divide the mass or percent by the relative atomic mass given
Divide that answer by the smallest answer found
Write the formula

Question 9

How to calculate percentage yield?

Answer 9

Amount of product collected
__________________________________ X 100
Maximum amount of product possible

Question 10

Possible reasons not to get maximum percentage yield?

Answer 10

Inaccuracies in experiment
Reaction is reversible
Reactants may react with unexpected chemicals (from the atmosphere)

Question 11

What is a reversible reaction?

Answer 11

The product of a chemical reaction can react to produce the reactants

Question 12

What are food additives?

Answer 12

Substances added to food to improve its qualities

Question 13

What method is used when checking food chemicals used are safe and analyse the colours?

Answer 13

Paper chromatography

Question 14

How does paper chromatography work?

Answer 14

A spot of colour is put onto paper and a solvent is allowed to move through the paper. The colours move different distances depending on their solubility

Question 15

What is the retention time?

Answer 15

The amount of time a substance spends in the column in gas chromatography

Question 16

What is a mass spectrometer?

Answer 16

Equipment used to detect and present the retention time and amount of a substance during gas chromatography. It is very quick, accurate and sensitive

Question 17

How does gas chromatography work?

Answer 17

The sample is vaporised and carried by a gas through a column where each chemical travels at different speeds, when leaving the column the mass spectrometer detects them and later, we can identify them against already known substances