Foundations in Chemistry

Question 1

What is relative atomic mass?

Answer 1

Weighted mean mass of an atom compared to 1/12th mass of an atom of Carbon-12

Question 2

What is relative isotopic mass?

Answer 2

Mass of an atom of an isotope compared with 1/12th mass of an atom of Carbon-12

Question 3

What is the formula of an Ammonium ion?

Answer 3

NH4+

Question 4

What is the formula of a carbonate ion?

Answer 4

CO3 2-

Question 5

What is an ionic compound?

Answer 5

A compound made up of oppositely charged ions held together by electrostatic forces

Question 6

What is the formula of a nitrate ion?

Answer 6

NO3-

Question 7

What is the formula of a sulfate ion?

Answer 7

SO4 2-

Question 8

What is atom economy?

Answer 8

A measure of the amount of starting materials that end up as useful products, a high atom economy means a process is more sustainable as there is less waste produced

Question 9

What is the equation for atom economy?

Answer 9

% atom economy = Mr of desired products / Sum of Mr of all products * 100

Question 10

What is avogadro’s constant?

Answer 10

Number of particles per mole of a substance (6.02*10^23)

Question 11

What is a dative covalent bond?

Answer 11

A type of bond where both electrons in the shared pair come from the same atom

Question 12

What is electronegativity?

Answer 12

The tendency of an atom to attract bonding electrons in a covalent bond

Question 13

What is the mass of an electron?

Answer 13

1/1836

Question 14

What is the mass number?

Answer 14

Number of protons and neutrons

Question 15

What is one use of heavy water?

Answer 15

Used to control processes in nuclear reactors

Question 16

What is a cation?

Answer 16

A positive ion, has fewer electrons than protons

Question 17

How many particles are there in 1 mole?

Answer 17

6.02*10^23

Question 18

What is empirical formula?

Answer 18

Simplest whole number ratio of atoms of each element in a compound

Question 19

What is a method to determine the water of crystallisation in hydrated crystals?

Answer 19

1. Weigh an empty crucible
2. Add the hydrated salt into the weighed crucible, weigh crucible and hydrated salt
3. Heat crucible, then heat strongly
4. Leave crucible to cool, then weigh the anhydrous salt

Question 20

What assumptions do you make when calculating water of crystallisation and what are solutions to these problems?

Answer 20

1. All of the water has been lost, heat to constant mass
2. No further decomposition, many salts decompose further when heated

Question 21

What is a standard solution?

Answer 21

A solution of known concentration

Question 22

How do you make up a standard solution?

Answer 22

Dissolving an exact mass of the solute in a solvent and making up the solution to an exact volume

Question 23

What is the molar gas volume at RTP?

Answer 23

24 dm3

Question 24

What is the ideal gas equation?

Answer 24

pV=nRT

Question 25

How do you convert from dm3 to m3?

Answer 25

Divide by 1000

Question 26

How do you convert from C to K?

Answer 26

+273

Question 27

How do you experimentally find a relative molecular mass of a volatile liquid?

Answer 27

1. Add a sample of the volatile liquid to a small syringe via a needle 2. Inject the sample into a gas syringe 3. Place gas syringe in a boiling water bath

Question 28

What is the method to calculating reacting masses/quantities?

Answer 28

1. Calculate the moles that reacts 2. Write out the equations and calculate the amount of moles formed 3. Calculate mass of product formed

Question 29

What is the method for identifying an unknown metal?

Answer 29

1. Weigh a sample of the metal and add to the flask 2. Using a measuring cylinder, add HCl to the flask and add the bung 3. Measure the max volume of gas in the syringe

Question 30

What is the method to calculating the Mr of the unknown metal?

Answer 30

1. From the experimental results the moles of H2 can be calculated 2. From the equation use the moles of H2 to calculate moles of X 3. Insert moles into mass/mr=mol equation

Question 31

What is theoretical yield?

Answer 31

Assuming all of the reactants are converted into products

Question 32

Why is it difficult to achieve maximum yield?

Answer 32

1. The reaction may not have gone to completion 2. Side reactions 3. Purification of the product may result in loss of some product

Question 33

What is the method to calculating percentage yield?

Answer 33

1. Calculate the amount of moles of the element that reacts (theoretical yield) 2. Use the equation to find the theoretical yield in moles 3. Calculate the actual yield in moles 4. Calculate the percentage yield

Question 34

What is the limiting reagent?

Answer 34

The reactant that is not in excess (used up first and stops the reaction)

Question 35

What is the atom economy of a chemical reaction?

Answer 35

A measure of how well atoms have been utilised

Question 36

Why are reactions with high atom economies good?

Answer 36

1. Produces a large proportion of desired products and few unwanted waste products 2. Important for sustainability as they make the best use of natural resources

Question 37

What is the method for calculating atom economy?

Answer 37

1. Write the equation and the Mr of the products 2. Calculate sum of desired products/sum of all products