Module 2 : Section 1

Question 1

Describe the structure of the atom

Answer 1

Orbitals: Hold electrons in place
Nucleus: Where you find protons and neutrons.
Contains most of the mass.

Question 2

Give the relative mass and relative charge of protons, neutrons and electrons.

Answer 2

Protons:
Mass = 1
Charge = +1
Neutrons:
Mass = 1
Charge = 0
Electrons:
Mass = 1/2000
Charge = -1

Question 3

What are isotopes?

Answer 3

Atoms of the same element with different numbers of neutrons.

Question 4

Define relative atomic mass.

Answer 4

Mean mass of an atom of an element, relative to 1/12th the mass of Carbon-12.

Question 5

Define isotopic mass.

Answer 5

Mass of an atom of an isotope of an element, relative tp 1/12th the mass of Carbon-12.

Question 6

How do you calculate the isotopic abundance of:
B-10 = 20%
B-11 = 80%

Answer 6

      100

Question 7

On a mass spectrum, what does the y axis and x axis show?

Answer 7

Y axis = Abundance of ions. Height of each peak gives you the relative isotopic abundance.
X axis = mass/charge. Can assume it is the relative isotopic mass.

Question 8

How would you calculate the relative atomic mass using data from a mass spectrum?

Answer 8

Multiply each relative isotopic mass by its relative isotopic abundance and add up the results. (X-axis value multiplied by its height)
Divide by the sum of the isotopic abundances (sum of the heights of the peaks)

Question 9

Give the equation linking mols, molar mass and mass.

Answer 9

mols = mass / molar mass

Question 10

Give the equation linking mols, volume and molar gas volume (24dm^3)

Answer 10

mols = volume/24 (dm^3)
mols = volume/24000 (cm^3)

Question 11

What is the ideal gas equation and what does it allow you to calculate?

Answer 11

pV = nRT 
allows you to calculate no of mols at any temperature or pressure.
p = pressure (Pa)
V = volume (m^3) 
1cm^3 = 1x10^-6 m^3
1dm^3 = 1x10^-3 m^3
n = no. of mols
R = 8.314
T = temperature (k) --> K= Degrees celsius + 273

Question 12

What is the empirical formula?

Answer 12

Smallest ratio of atoms of each element in a compound.

ALWAYS MEASURED IN MOLS

Question 13

What is molecular formula?

Answer 13

Actual no. of atoms of each element in a molecule.

Question 14

How are ions formed?

Answer 14

Ions are formed when electrons are transferred from one atom to another.

Question 15

Give the formula of the following molecular ions:

1. NItrate
2. Carbonate
3. Sulfate
4. Hydroxide
5. Ammonium
6. Zinc ion
7. Silver ion

Answer 15

1. NItrate = NO3 ^1-
2. Carbonate = CO3 ^ 2-
3. Sulfate = SO4 ^2-
4. Hydroxide = OH ^1-
5. Ammonium = NH4 ^1+
6. Zinc ion = Zn ^2+
7. Silver ion = Ag ^1+

Question 16

What are salts?

Answer 16

Salts are ionic compounds.

Solid salts have a lattice of +ve and -ve ions.

Question 17

What does a hydrated salt tell you?

Answer 17

It has waters of crystallisation attached to it.

Question 18

What is an anhydrous salt?

Answer 18

A salt that does not contain waters of crystallisation.

Question 19

How do you calculate the number of waters of crystallisation and formula of a hydrated salt.

Answer 19

1. Find mols of water lost.
2. Find mols of anhydrous salt.
3. Calculate ratio of mols in anhydrous salt to mols of water in the form 1:n

Question 20

?What is the main difference between acids and bases

Answer 20

Acids are proton (H+) donors

Bases are proton (H+) acceptors.

Question 21

Give the name and formula of 4 common acids.

Answer 21

Hydrochloric acid HCl
Sulfuric acid H2SO4
Nitric acid HNO3
Ethanoic acid CH3COOH

Question 22

Give the name and formula of 3 common bases.

Answer 22

Sodium Hydroxide NaOH
Potassium Hydroxide KOH
Ammonia NH3

Question 23

When acids and bases react, how is water formed?

Answer 23

H+ ions released by the acid and OH- ions released by the base combine to form
OH- + H+ —> H20

Question 24

When acids and bases react, how is the salt formed?

Answer 24

When the H+ ions in the acid are replaced by metal ions or ammonium ions from the alkali
HCl + KOH —> KCl + H2O

Question 25

Describe the set up of equipment for performing a titration.

Answer 25

Measure out the alkali in a pipette to the line. Let the alkali drop down into the conical flask and add an indicator. Put the conical flask underneath a burette containing the acid, which allows you to add the acid drop by drop.

Question 26

Describe the procedure of doing a titration.

Answer 26

1. First do a rough titration, to get an idea of the end point. 2. Do an accurate titration, run the acid within 2cm^3 of the endpoint, then add the acid dropwise (drop by drop) 3. Calculate the titre ( final reading - initial reading) 4. Repeat the titration and calculate a mean, ignoring any anomalous results. 5. Remember to wash out the conical flask, to remove any acid or alkali.

Question 27

How can you make a titration accurate?

Answer 27

When taking a reading from a burette, you should read from the bottom of the meniscus.

Question 28

What is an analyte?

Answer 28

Solution of unknown concentration.

Question 29

What is a standard solution?

Answer 29

Solution with a known concentration. Made by dissolving a known amount of solid in a known amount of water.

Question 30

How do you make up a standard solution?

Answer 30

1. Using a precise balance, weigh out the required mass of solid. 2. Transfer to a beaker. Use distilled water to wash and bits of solid from the watch glass. 3. Add water to completely dissolve the solid. Use a glass rod to stir the solution. 4. Once dissolved, transfer into a volumetric flask. 5. Fill volumetric flask up to graduation line. 6. Put lid on the flask and turn in over to thoroughly mix it.

Question 31

Give the equation linking mols, concentration and volume.

Answer 31

mols = conc x vol

Question 32

Give the equation for % yield.

Answer 32

Actual yield / theoretical yield x 100 | MOLS

Question 33

Give the equation for Atom Economy.

Answer 33

Mr of desired product / Mr of all products x 100

Question 34

Give an example of a reaction which has a 100% Atom economy.

Answer 34

Addition reaction, as only 1 product is made. | C2H4 + H2 ---> C2H6

Question 35

What does % yield tell you?

Answer 35

It tells you how wasteful the process is.

Question 36

What does Atom Economy tell you?

Answer 36

Tells you the sustainability of reactions.

Question 37

What is the oxidation number of Oxygen?

Answer 37

-2

Question 38

What is the oxidation number of Hydrogen?

Answer 38

+1

Question 39

What is oxidation?

Answer 39

Loss of electrons

Question 40

What is reduction?

Answer 40

Gain of electrons.

Question 41

What do oxidising agents do?

Answer 41

They accept electrons and get reduced.

Question 42

What do reducing agents do?

Answer 42

They donate electrons and get oxidised.