Topic 2 - Atoms, Molecules, and Stoichiometry

Question 1

What is an atom mostly made of?

Answer 1

Empty space.

Question 2

What does the proton (atomic) number tell you?

Answer 2

The number of protons and electrons in an atom.

Question 3

What does the mass number tell you?

Answer 3

The number of protons and neutrons in the nucleus of an atom

Question 4

What is Relative Atomic Mass?

Answer 4

The weighted mean mass of an atom of an element, compared to 1/12th of the mass of an atom of Carbon-12.

Question 5

What is Relative Isotopic Mass?

Answer 5

The mass of an atom of an isotope compared to 1/12th of the mass of an atom of Carbon-12.

Question 6

What is Relative Molecular Mass?

Answer 6

The mean mass of a molecule compared to 1/12th of the mass of an atom of Carbon-12.

Question 7

What are the two types of reaction equations?

Answer 7

Word and symbol.

Question 8

What are the two parts of an equation?

Answer 8

The reactants and the products.

Question 9

What is normally written above or below the arrow in equations?

Answer 9

A catalyst or practical conditions.

Question 10

What are ionic equations?

Answer 10

Equations that show the ions that are formed in solution and show which particles are reacting.

Question 11

What substances normally form ions in solution?

Answer 11

Acids, bases, and salts.

Question 12

What are spectator ions?

Answer 12

Ions that don’t get involved in the reaction and don’t change.

Question 13

What are the four state symbols?

Answer 13

(s) - Solid
(g) - Gas
(l) - Liquid
(aq) - Aqueous

Question 14

What is a displacement reaction?

Answer 14

When a more reactive element takes the place of a less reactive element in a compound.

Question 15

What do acids and bases form?

Answer 15

Salt and water.

Question 16

What do carbonates also form in acids and bases reactions?

Answer 16

Carbon dioxide.

Question 17

What is a precipitation reaction?

Answer 17

When a solid is formed is produced after 2 aqueous reactants react.

Question 18

What are the three cations you need to know?

Answer 18

NH4^+ - Ammonium
Zn^2+ - Zinc (II)
Ag^+ - Silver (I)

Question 19

What are the six anions you need to know?

Answer 19

SO4^2- Sulphate
CO3^2- Carbonate
HCO3^- Hydrogencarbonate
OH- Hydroxide
NO3 ^- Nitrate
PO4^3- Phosphate

Question 20

What is Avogadro’s number (L)?

Answer 20

6.02x10^23

Question 21

What is the formula to calculate the number of particles in a substance?

Answer 21

no. of particles = Avogadro’s number x no. of moles

Question 22

What is the formula to calculate the mass of a substance using Ar or Mr?

Answer 22

No. of moles = mass (grams) / Mr or Ar

Question 23

How do you convert m to dm to cm?

Answer 23

Multiply by 10 for each jump.

Question 24

When converting units, how do you change the number you multiply for each dimension?

Answer 24

Add a 0 for each dimension added.
e.g. dm - cm = x10
dm^2 - cm^2 = x 100
dm^3 - cm^3 = x 1000

Question 25

What is the formula to calculate the number of moles of a substance in solution?

Answer 25

No. of moles = concentration x volume

Question 26

What are the units for concentration?

Answer 26

moldm^-3

Question 27

What are the units for volume?

Answer 27

dm^3

Question 28

What is the empirical formula?

Answer 28

The simplest whole number ratio of elements in a compound.

Question 29

What are the four steps to finding the empirical formula for a compound?

Answer 29

1. Write out the elements involved. 2. Write the percentages as masses. 3. Divide these by Relative Atomic Mass to get number of moles. 4. Divide all the numbers by the smallest number of moles.

Question 30

How do you find the molecular formula from the empirical formula?

Answer 30

Mr of empirical formula / Mr of molecular formula = y Multiply all the atoms in the empirical formula by y.

Question 31

What are the 4 steps for finding the water of crystallisation?

Answer 31

1. Write out the 2 molecules involved. 2. Write the masses of each molecule. 3. Divide these by Relative Molecular Mass to get number of moles. 4. Divide all the numbers by the smallest number of moles.

Question 32

What are the three steps to using equations to work out theoretical masses?

Answer 32

1. Write out equation and balance it. 2. Work out Mr/Ar of species involved. Write these as mass in g. 3. Divide the reactant to find 1g and multiply it by the mass given in the question. Do the exact same to the other side to work out the theoretical mass produced.

Question 33

What is the equation for finding the number of moles in a gas equation?

Answer 33

No. of moles = volume / molar gas volume

Question 34

What is the molar gas volume?

Answer 34

The volume a mole of gas occupies measured in dm^3mol^-1

Question 35

At standard room temperature and pressure, what is the molar gas volume for any gas?

Answer 35

24dm^3mol^-1

Question 36

At standard temperature and pressure, what is the molar gas volume for any gas?

Answer 36

22.4dm^3mol^-1

Question 37

What is standard room temperature and pressure?

Answer 37

293K, 101.3kPa

Question 38

What is standard temperature and pressure?

Answer 38

273K, 101.3kPa