Non-Wolsey Study

Question 1

Atomic mass is the

Answer 1

weighted average mass of an atom compared to C-12 (having 12 units)

Question 2

Molecular mass is

Answer 2

the mass of a molecule compared to C-12 which has 12 units on the scale

Question 3

Formula mass is

Answer 3

the mass of one formula unit of a compound compared to C-12 having 12 units on the scale

Question 4

Isotopic mass

Answer 4

Mass of a particular isotope of an element compared to C-12 having 12 units on the scale

Question 5

Define the term “Mole”

Answer 5

The amount of substance that has the same number of particles as there are atoms in exactly 12g of carbon-12 isotope.

1 Mole (mol) has exactly 6.02x10/\23 particles.

Question 6

What is Avogadro’s constant

Answer 6

The number of atoms, ions, molecules or electrons in a Mole = 6.02x10/\23

Question 7

Define “Empirical Formula”

Answer 7

gives the simplest ratio of different atoms present in a molecule

Question 8

Define “Molecular Formula”

Answer 8

gives actual numbers of each type of atoms in a molecule

Question 9

What is the triangle formula involving Mass, Molar Mass and Moles

Answer 9

M=m/n

Molar mass = Mass/Number of Moles

Question 10

How do you calculate the volume of a gas at room temp.?

Answer 10

Moles x 24

At room temperature

Question 11

What is the unit of volume of gas

Answer 11

dm/\3

1000cm/\3 = 1dm/\3

Question 12

Triangle formula for concentration

Answer 12

C=n/V

Concentration = Number of Moles/Volume

Question 13

Unit of concentration

Answer 13

mol dm/-3

Question 14

What is this unit for: mol dm/-3

Answer 14

Concentration

Question 15

Steps to calculate relative atomic mass from isotpoic mass and abundance

Answer 15

1. Multiply each isotopic mass with its abundance %
2. Add all the figures together
3. Divide by 100

Question 16

The formula for __ ______ compound is always its empirical formula

Answer 16

an ionic

Question 17

The molecular formula for simple inorganic compounds are often…

Answer 17

the same

Question 18

Organic molecules often have ________ empirical and molecular formulae

Answer 18

different

Question 19

Organic compounds must be very ____ for combustion to calculate _______ ________

Answer 19

very pure, to calculate empirical formula

Question 20

Steps for Empirical formula of magnesium oxide- compositional mass (0.486g)

Answer 20

1. Burn known mass of Mg in excess oxygen (0.486g)
2. Record the mass of Mg oxide formed (0.806g)
3. Calculate the mass of the oxygen (0.806g - 0.486g) = 0.320g
4. Calculate the mole ratio of Mg to O
   Moles of Mg = 0.486/24.3 mol/-1 = 0.0200
   Moles of O = 0.320/16.0 mol/-1 = 0.0200

Simplest ratio is 1:1 - Therefore empirical formula is MgO

Question 21

Steps for empirical formula - combustion

Answer 21

1. Note the mass of each element.
2. Divide by atomic masses.
3. Divide both by lowest figure.
4. Empirical formula is the lowest whole number ratio.

Question 22

What are spectator ions

Answer 22

Ions in an ionic reaction that do not interact - they are not included in ionic equations.

Question 23

Balancing/writing ionic equations - Steps

Answer 23

1. Write the full balanced equation
2. Write down the ions present. (Any compounds are broken down into each element, and their charges are found by looking at the periodic table. Grp 1 = +, Grp 2 = 2+, Grp 6 = 2-, Grp 7 = -.
3. Cancel out ions that appear the same on each side of equation (spectator ions)
4. Re-write equation without the spectator ions

Question 24

Steps for calculating concentration when given mass in g and volume in cm/\3.

Answer 24

1. Change g to mol (g/Mr)
2. Change cm3 to dm3 (cm/1000)
3. Calculate concentration:

Number of moles in solute (mol)
——————————————- = concentration (mol dm3)
Volume of solution (dm-3)

Question 25

Steps for calculating mass from concentration

Answer 25

1. Re-arrange concentration equation to find number of moles (mol)
   n (mol) = concentration (mol dm-3) x volume (dm3)
2. Multiply moles of solute by its molar mass
   m of solute (g) = n (mol) x M (g mol-1)

Question 26

Calculate mole ratio

Answer 26

mass/atomic mass

Divide both answers by the smallest answer and that is the mole ration.

Usually like them both to be whole numbers