Part One: Multiple Choice

$$
\text{Mass} = \text{Moles} \times \text{Molar mass}
$$
$$
\text{Mass} = 2 \text{ mol} \times 44 \text{ g/mol} = 88 \text{ g}
$$
The correct option is **c) 88 grams**.

The $\text{Ca}^{2+}$ ion has lost 2 electrons.
$$
\text{Number of electrons} = 20 - 2 = 18 \text{ electrons}
$$
The correct option is **b) 18 electrons**.

$$
\text{Mass percent of Ca} = \left( \frac{\text{Mass of Ca}}{\text{Molar mass of CaO}} \right) \times 100\%
$$
$$
\text{Mass percent of Ca} = \left( \frac{40 \text{ g/mol}}{56 \text{ g/mol}} \right) \times 100\%
$$
$$
\text{Mass percent of Ca} \approx 0.71428 \times 100\% \approx 71.4\%
$$
The closest option is **a) 72.4%**.

$$
\text{Molar mass of HCl} = (\text{RAM of H} \times 1) + (\text{RAM of Cl} \times 1)
$$
$$
\text{Molar mass of HCl} = (1 \times 1) + (35.5 \times 1) = 1 + 35.5 = \boxed{\text{36.5 g/mol}}
$$

**b)** How many moles are there in $7 \text{ g}$ of $\text{HCl}$?

$$
\text{Moles} = \frac{\text{Mass}}{\text{Molar mass}}
$$
$$
\text{Moles of HCl} = \frac{7 \text{ g}}{36.5 \text{ g/mol}} \approx \boxed{\text{0.192 mol}}
$$

**c)** How many grams are there in $5 \text{ moles}$ of $\text{HCl}$?

$$
\text{Mass} = \text{Moles} \times \text{Molar mass}
$$
$$
\text{Mass of HCl} = 5 \text{ mol} \times 36.5 \text{ g/mol} = \boxed{\text{182.5 g}}
$$

**b)** State the number of neutrons of the three atoms:  
The number of neutrons is calculated as Mass Number - Atomic Number.
*   Atom A: Neutrons = $24 - 12 = \boxed{\text{12 neutrons}}$.
*   Atom B: Neutrons = $12 - 6 = \boxed{\text{6 neutrons}}$.
*   Atom C: Neutrons = $56 - 26 = \boxed{\text{30 neutrons}}$.

**c)** What name is given to atoms of the same element but different mass numbers?  
The name given to atoms of the same element (same number of protons) but different mass numbers (different number of neutrons) is **Isotopes**.

**b)** Which one has a higher boiling point, chlorine or iodine?  
From the table:
*   Chlorine boiling point: $-34^\circ\text{C}$
*   Iodine boiling point: $184^\circ\text{C}$
**Iodine** has a higher boiling point than chlorine.

**c)** What happens to the size of the atoms as we go down the group?  
As you move down Group 7, the size of the atoms **increases**. This is because additional electron shells are added, and the increased shielding reduces the effective nuclear charge on the outermost electrons, causing them to be held less tightly and further from the nucleus.

**b)** Name the type of bond formed when these atoms react.  
Sodium (a metal) reacts with chlorine (a non-metal) by transferring an electron from sodium to chlorine. This forms an **ionic bond**.

**c)** Why do ionic compounds have a higher melting and boiling points than simple molecular compounds?  
Ionic compounds have strong electrostatic forces of attraction between the positively and negatively charged ions in their crystal lattice. A large amount of energy is required to overcome these strong forces, resulting in high melting and boiling points. Simple molecular compounds, on the other hand, have weak intermolecular forces that require much less energy to overcome.

**b)** What do we mean by the term copolymer?  
A copolymer is a polymer formed from **two or more different types of monomers**.

**c)** Give one example of a natural polymer and one example of a synthetic polymer.
*   Natural polymer: **Cellulose** (or starch, proteins, DNA).
*   Synthetic polymer: **Polyethylene** (or PVC, nylon, polyester).

**d)** What are the two types of polymerization reactions?  
The two main types of polymerization reactions are **addition polymerization** and **condensation polymerization**.

**b)** Calculate the mass percent of calcium in $\text{CaCO}_3$.
$$
\text{Mass percent of Ca} = \left( \frac{\text{Mass of Ca}}{\text{Molar mass of CaCO}_3} \right) \times 100\%
$$
$$
\text{Mass percent of Ca} = \left( \frac{40 \text{ g/mol}}{100 \text{ g/mol}} \right) \times 100\% = \boxed{\text{40%}}
$$

**c)** Calculate the mass percent of Oxygen in $\text{CaCO}_3$.
$$
\text{Mass percent of O} = \left( \frac{\text{Mass of O in CaCO}_3}{\text{Molar mass of CaCO}_3} \right) \times 100\%
$$
$$
\text{Mass percent of O} = \left( \frac{3 \times 16 \text{ g/mol}}{100 \text{ g/mol}} \right) \times 100\% = \left( \frac{48 \text{ g/mol}}{100 \text{ g/mol}} \right) \times 100\% = \boxed{\text{48%}}
$$

**b)** Write down the half-equation of reactions at each electrode:
*   At the anode (oxidation): Negative bromide ions lose electrons.
    $$
    \text{2Br}^- \to \text{Br}_2 + \text{2e}^-
    $$
*   At the cathode (reduction): Positive lead ions gain electrons.
    $$
    \text{Pb}^{2+} + \text{2e}^- \to \text{Pb}
    $$

**c)** State any two uses of electrolysis.
1.  **Electroplating**: Used to coat metals with a thin layer of another metal for decorative purposes or to prevent corrosion.
2.  **Extraction of metals**: Used to extract reactive metals (e.g., aluminum, sodium) from their ores.
3.  **Purification of metals**: Used to purify metals like copper.

**b)** State the catalyst used in the above process.  
The catalyst used is **Manganese dioxide ($\text{MnO}_2$)**.

**c)** Write down a balanced chemical equation for the reaction in the above process.
$$
\text{2H}_2\text{O}_2 \xrightarrow{\text{MnO}_2} \text{2H}_2\text{O} + \text{O}_2
$$

**b)** Which substance remains in the evaporation dish?  
The substance that remains in the evaporation dish is the **salt**.

**c)** What happens to the water during these processes?  
The water **evaporates** (changes from liquid to gas) and leaves the system.

**b)** What happens to the anode during the electroplating process?  
In electroplating, if the anode is made of the metal to be deposited (e.g., copper anode for copper plating), the anode **dissolves**, releasing metal ions into the electrolyte solution. These ions then migrate to the cathode to be deposited.

**c)** List any two uses of electroplating.
1.  **Decorative purposes**: To coat objects with precious metals like gold or silver to improve their appearance.
2.  **Corrosion protection**: To apply a protective layer of a less reactive metal (e.g., chromium, nickel) onto a more reactive metal to prevent rust and corrosion.
3.  **Enhancing properties**: To improve hardness, wear resistance, or electrical conductivity of a surface.