9 (a) An aluminum atom has the atomic number 13 and the mass number 27 - Edexcel - GCSE Chemistry - Question 9 - 2019 - Paper 1

To calculate the maximum mass of magnesium oxide (MgO) formed, we first need to find out how many moles of magnesium we have:

1. The molar mass of Mg is 24.0 g/mol.

2. The moles of magnesium can be calculated as follows:

   $ext{Moles of Mg} = \frac{\text{mass}}{\text{molar mass}} = \frac{1.35 g}{24.0 g/mol} = 0.05625 mol$

3. From the balanced equation, 2 moles of Mg produce 2 moles of MgO. Therefore, the moles of MgO formed will be equal to the moles of magnesium used:

   $\text{Moles of MgO} = 0.05625 mol$

4. The molar mass of MgO (Mg = 24.0 g/mol, O = 16.0 g/mol) is:

   $\text{Molar mass of MgO} = 24.0 + 16.0 = 40.0 g/mol$

5. Finally, to find the mass of MgO formed:

   $\text{Mass of MgO} = \text{Moles} \times \text{Molar mass} = 0.05625 mol \times 40.0 g/mol = 2.25 g$

Thus, the maximum mass of magnesium oxide that could be formed is 2.25 g.

The balanced equation for the reaction between chlorine (Cl₂) and hydrogen (H₂) to form hydrogen chloride (HCl) is:

$Cl_2 + H_2 \rightarrow 2HCl$

Sodium chloride (NaCl) is formed when sodium (Na) and chlorine (Cl) combine. The electronic configuration of sodium is 2.8.1, and that of chlorine is 2.8.7.

1. Ion Formation: Sodium has one electron in its outer shell and readily loses that electron to achieve a full outer shell (2.8). This loss results in the formation of a sodium ion (Na⁺), which has a positive charge:

   $Na \rightarrow Na^+ + e^-$

Chlorine has seven electrons in its outer shell and needs one more to complete it. It gains the electron from sodium, forming a chloride ion (Cl⁻) with a negative charge:

$Cl + e^- \rightarrow Cl^-$

2. Ionic Bonding: The oppositely charged ions (Na⁺ and Cl⁻) attract each other, forming an ionic bond.

3. Arrangement in Solid State: In solid sodium chloride, these ions are arranged in a crystal lattice structure, where each sodium ion is surrounded by six chloride ions and vice versa. This regular arrangement maximizes the electrostatic attraction between the oppositely charged ions.