What is the shape of an ammonia (NH₃) molecule? (d) The following equation shows the heat of reaction for the formation of benzene: $$C(s) + \frac{3}{2}H_2(g) \rightarrow C_6H_6(l) \qquad \Delta H = 49.1 \text{ kJ mol}^{-1}$$ Is this reaction exothermic or endothermic? Explain your answer - Leaving Cert Chemistry - Question c - 2014

The given reaction is endothermic. This is indicated by the positive value of \Delta H = 49.1 kJ mol^{-1}, which means that energy is absorbed during the reaction. In exothermic reactions, \Delta H would be negative, indicating that energy is released.

The attraction of the liquid towards the charged plastic rod indicates that the liquid has polar bonding. This is because polar molecules have a positive and a negative end, allowing them to be influenced by an external electric field.

Chlorine is added to swimming pool water primarily as a disinfectant. It kills harmful bacteria and microorganisms, ensuring the water remains clean and safe for swimming.

The particles that carry electric current through a solution during electrolysis are ions. These charged particles move towards the electrodes, allowing the flow of electric current.

The type of nuclear radiation that consists of positively-charged particles identical to helium nuclei is called alpha radiation.

To calculate the percentage by mass of sulfur in sulfur trioxide (SO₃), we start by determining the molar mass:

• Molar mass of S = 32.07 g/mol
• Molar mass of O = 16.00 g/mol

Molar mass of SO₃ = 32.07 g/mol (S) + 3 × 16.00 g/mol (O) = 32.07 g/mol + 48.00 g/mol = 80.07 g/mol.

Now, the percentage of sulfur by mass is given by:

$\text{Percentage of S} = \left( \frac{32.07}{80.07} \right) \times 100 \approx 40.0\%$