## 1.) The volume of a sample of gas measured at 27 C is 14.0 dm3. What is the temperature when the volume is reduced to 13.0 dm3 at the same pressure?

A.) 5
B.) 3
C.) 7
D.) 8

V1/T1 = V2/T2 | Converting celsius to kelvin – 27 celsius to 300 K
15/300 = 14/T
T = (14*300) / 15 = 280K converted to celsius is 6.85 C (280 – 273.15 = 6.85 C)

## 2.) 20 g of bromine reacts with 4.3 g of metal, M, to form MBr2. What is the relative atomic mass of the metal M? (Ar :Br = 80)

A.) 34
B.) 28
C.) 17
D.) 64

Relative atomic mass = (A / Mass of Bromine) * (Mass of metal) = (80*2 / 20) * 4.3
= (160/20)*4.3 = 34

## 3.) What is the concentration, in mol dm3, of 30.0 g of NaOH (Mr = 40.0) in 150.0 cm3?

A.) 0.05
B.) 5
C.) 50
D.) 0.5

To find the moles, = mass of substance / molecular mass = 30/40 = 0.75 moles
Concentration = moles / dm3 = 0.75 / 0.15 = 5 mol/dm3

## 4.) Which one is correct for 1222Mg2+ ?

A.) Protons: 12 Neutrons: 10 Electrons: 12
B.) Protons: 14 Neutrons: 14 Electrons: 8
C.) Protons: 12 Neutrons: 10 Electrons: 12
D.) Protons: 12 Neutrons: 10 Electrons: 10

Since it is a cation (2+), it loses 2 electrons hence making the electron number 10.

## 5.) How do the following properties change down Group 2 of the periodic table?

A.) Ionization energy increases
C.) Melting point decreases
D.) Boiling point increases

Down any group, the number of energy levels (n) increases, so there is a greater distance between the nucleus and the outermost orbital. This results in a larger atomic radius.

## 6.) Which species will require the least energy for the removal of one electron?

A.) Ca+
B.) Mg2+
C.) Na+
D.) Al2+

Ca+ has more protons in the nucleus, meaning there is a weaker attraction between the nucleus and the electron to be removed, meaning less energy is required to remove it.

## 7.) Which compound has hydrogen bonds between its molecules?

A.) CH2O
B.) CH4
C.) C2H4
D.) CH4O

CH4O is the only molecule that has a hydrogen bonding between O and H. The other molecules have bonds between C and H which are not considered hydrogen bonds. Hydrogen bonds results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a N, O, or F atom

## 8.) Why is the pH of unpolluted rain less than 7?

A.) Nitrogen oxides
B.) Sulfur dioxide
C.) Carbon dioxide
D.) Methane

Unpolluted rain has a slightly acidic pH of 5.6, because carbon dioxide and water in the air react together to form carbonic acid, a weak acid.

## 9.) Which molecule is polar?

A.) Cl2
B.) CO2
C.) CH4
D.) H2O

Water (H2O) is polar because of the bent shape of the molecule. The shape means most of the negative charge from the oxygen on one side of the molecule and the positive charge of the hydrogen atoms is on the other side of the molecule.

## 10.) What increases the activation energy of a molecule?

A.) Decreasing temperature
B.) Increasing concentration
D.) Decreasing collision frequency

With an increase in concentration, the number of molecules with the minimum required energy will increase, and therefore the rate of the reaction will increase. Adding a catalyst, decreasing the temperature and collision frequency will reduce the activation energy.

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