3-Atomic Structure+Equations

Question 0

What does the atomic number tell you?

Answer 0

The number of protons and electrons in the element.

Question 1

What is the equation for finding the number of neutrons?

Answer 1

no. of neutrons = mass no. - atomic no.

Question 2

What is the relative mass of a proton, neutron and electron?

Answer 2

Proton = 1
Neutron = 1
Electron = almost nothing/0

Question 3

What is a isotope?

Answer 3

Atoms of the same element with different numbers of neutrons. The have the same atomic number but different mass numbers.

Question 4

What is the relative atomic mass (Ar)?

Answer 4

The mass number.

Question 5

How do you find the relative formula mass (Mr)?

Answer 5

By adding the relative atomic mass/mass number of each element in the compound. Eg if it was H2O then it would be (2x1) + 16 = 2 + 16 = 18 <— relative formula mass.

Question 6

What is the formula to find the percentage mass?

Answer 6

Relative mass of element in 
            compound
————————————x100
Relative formula mass of 
             compound

Question 7

How do you find the empirical formula of a compound?

Answer 7

1. Identify actual masses of elements in the compound.
2. Divide these masses by their relative atomic masses.
3. Divide each of these by the smallest to get the ratio.
4. If ratio doesn’t work out a whole numbers then multiply each number by the same factor to get whole numbers.

Question 8

What is the mass of one mole of each element?

Answer 8

It’s the relative atomic mass in grams.

Question 9

What is the mass of a mole of a compound in grams?

Answer 9

It’s the relative formula mass in grams.

Question 10

What is the equation to find out how many moles of an element you have?

Answer 10

Mass
Moles=———————
Relative formula
mass

Question 11

How do you calculate the mass of a product?

Answer 11

1. Write down the equation.
2. Work out the relative formula mass of each substance.
3. Check total mass of reactants is equal to total mass of products.
4. Check what question asks you and put into ratio accordingly.
   Eg. CaCO3 —> CaO + CO2
   40+12+(3x16) —> (40+16)+(12+(2x16))
   100 —> 56+44
   100:56 (44 not wanted in question)

Question 12

How do you calculate the mass of a reactant?

Answer 12

1. Write down the equation.
2. Work out the relative formula mass of each substance.
3. Check total mass of reactants equals total mass of products.
4. Check what question asks you and put into ratio accordingly.
   Eg. 2 x Al2O3 —> 4 x Al + 3 x O2
   2((2x27)+(3x16)) —> (4x27)+(3x(2x16))
   204 —> 108+96
   204:108 (96 not wanted in question)

Question 13

What is the equation for working out the percentage yield?

Answer 13

Yield from reaction
—————————x100
Maximum theoretical
yield

Question 14

What is a reversible reaction?

Answer 14

A reaction in which the products can react to produce the original reactants.

Question 15

What is chromatography?

Answer 15

Used to identify artificial colours by comparing the unknown substances to known ones.

Question 16

How would you do a chromatography experiment?

Answer 16

1. Samples of 4 known and one unknown put on a pencil line on chromatography paper.
2. Paper stood in solvent below the pencil line.
3. Solvent travels up the paper and dissolves samples, carrying them up the paper as well.
4. Samples travel by different amounts due to different solubilities. Unknown sample compared to the known ones.

Question 17

What is gas chromatography for?

Answer 17

Used to separate and identify mixtures.

Question 18

How does gas chromatography work?

Answer 18

A mixture of compounds is carried by gas through a column packed with powdered material.
The compounds travel at different speeds and this causes them to separate.

Question 19

What does the chromatogram show?

Answer 19

• number of compounds present by number of peaks
• how much of each compound there is by the size of the peak
• retention time by the position of the peak

Question 20

What is the retention time for a gas chromatography machine?

Answer 20

The amount of time taken for the compound to go through the machine.

Question 21

What is a mass spectrometer?

Answer 21

Something often attached to a gas chromatography machine that allows substances leaving the column to be identified.

Question 22

Why are mass spectrometers useful?

Answer 22

They identify substances very quickly and accurately even in small quantities. Can also give the relative formula mass of each substance separated by gas chromatography if used together. Usually identify the relative formula mass of the compound from the bar on the far right.

Question 23

Why do research scientists measure amounts of materials used and produced?

Answer 23

To make sure it’s economical, if all reactants aren’t converted into useful products there will be waste and the sell on price may be raised. This will impact on the retail price of the final products.
Also, to meet the present needs of people without spoiling the environment, sustainable development.

Question 24

Why does the chemical industry examine its processes?

Answer 24

To make sure that it:

• makes efficient use of energy
• reduces the hazards and risks of chemicals used and produced
• reduces waste
• attempts to convert a high proportion of the atoms in the reactants into products
• uses mainly renewable sources
• prevents pollution of environment