When 50cm³ of 2M HCl was neutralised by an equal volume of 2M NaOH, it initially rose to a minimum of 33.7°C. What is the molar enthalpy of neutralisation of NaOH?

Question

Asked on June 1, 2026Chemistry

This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.

Accepted Answer · 2026-06-01T18:17:42.448Z

1) Molar enthalpy of neutralization Step 1: Calculate the heat absorbed by the solution. The total volume of the solution is 50 cm^3 + 50 cm^3 = 100 cm^3. Assuming the density of the solution is 1 g/cm^3, the mass of the solution is 100 g. The change in temperature is T = 33.7 °C - 20 °C = 13.7 °C. The specific heat capacity is 4.2 kJ kg^-1 K^-1, which is equivalent to 4.2 J g^-1 K^-1. Q = mc T Q = (100 g) × (4.2 J g^-1 K^-1) × (13.7 K) Q = 5754 J = 5.754 kJ Step 2: Calculate the moles of reactant. Moles of HCl = Concentration × Volume (in dm³) Moles of HCl = 2 M × (50/1000) dm^3 = 2 M × 0.050 dm^3 = 0.10 mol The neutralization reaction is HCl(aq) + NaOH(aq) NaCl(aq) + H_2O(l). The mole ratio is 1:1, so 0.10 mol of neutralization occurred. Step 3: Calculate the molar enthalpy of neutralization. The heat released is Q = 5.754 kJ. Since the temperature increased, the reaction is exothermic, so the enthalpy change is negative. H_neut = -(Q)/(moles) H_neut = -5.754 kJ0.10 mol H_neut = -57.54 kJ mol^-1 The molar enthalpy of neutralization of NaOH is -57.54 kJ mol^-1. 2) Draw and name two positional isomers of alkanol C₄H₉OH. Positional isomers have the same molecular formula and carbon skeleton but differ in the position of the functional group. Isomer 1: The hydroxyl group (-OH) is on the first carbon atom. CH_3CH_2CH_2CH_2OH Name: Butan-1-ol Isomer 2: The hydroxyl group (-OH) is on the second carbon atom. CH_3CH_2CH(OH)CH_3 Name: Butan-2-ol 3) Explain why metals such as Mg and Al are good conductors of electricity. Metals like magnesium and aluminum are good conductors of electricity because they contain delocalized electrons. These valence electrons are not fixed to individual atoms but are free to move throughout the entire metallic structure. When an electric potential difference is applied, these mobile electrons can easily flow, carrying electric charge and thus conducting electricity. 4) Give a reason why Al is preferred to Mg for making cooking pans. Aluminum is preferred over magnesium for making cooking pans primarily due to its superior corrosion resistance. Aluminum forms a thin, tough, and impermeable layer of aluminum oxide (Al₂O₃) on its surface when exposed to air, which protects the underlying metal from further corrosion, especially from acids found in food. Magnesium is more reactive and can corrode more easily, particularly in the presence of water or acids at cooking temperatures. Send me the next one 📸

Accepted Answer · 2026-06-01T18:17:42.448Z

1) Molar enthalpy of neutralization Step 1: Calculate the heat absorbed by the solution. The total volume of the solution is 50 cm^3 + 50 cm^3 = 100 cm^3. Assuming the density of the solution is 1 g/cm^3, the mass of the solution is 100 g. The change in temperature is T = 33.7 °C - 20 °C = 13.7 °C. The specific heat capacity is 4.2 kJ kg^-1 K^-1, which is equivalent to 4.2 J g^-1 K^-1. Q = mc T Q = (100 g) × (4.2 J g^-1 K^-1) × (13.7 K) Q = 5754 J = 5.754 kJ Step 2: Calculate the moles of reactant. Moles of HCl = Concentration × Volume (in dm³) Moles of HCl = 2 M × (50/1000) dm^3 = 2 M × 0.050 dm^3 = 0.10 mol The neutralization reaction is HCl(aq) + NaOH(aq) NaCl(aq) + H_2O(l). The mole ratio is 1:1, so 0.10 mol of neutralization occurred. Step 3: Calculate the molar enthalpy of neutralization. The heat released is Q = 5.754 kJ. Since the temperature increased, the reaction is exothermic, so the enthalpy change is negative. H_neut = -(Q)/(moles) H_neut = -5.754 kJ0.10 mol H_neut = -57.54 kJ mol^-1 The molar enthalpy of neutralization of NaOH is -57.54 kJ mol^-1. 2) Draw and name two positional isomers of alkanol C₄H₉OH. Positional isomers have the same molecular formula and carbon skeleton but differ in the position of the functional group. Isomer 1: The hydroxyl group (-OH) is on the first carbon atom. CH_3CH_2CH_2CH_2OH Name: Butan-1-ol Isomer 2: The hydroxyl group (-OH) is on the second carbon atom. CH_3CH_2CH(OH)CH_3 Name: Butan-2-ol 3) Explain why metals such as Mg and Al are good conductors of electricity. Metals like magnesium and aluminum are good conductors of electricity because they contain delocalized electrons. These valence electrons are not fixed to individual atoms but are free to move throughout the entire metallic structure. When an electric potential difference is applied, these mobile electrons can easily flow, carrying electric charge and thus conducting electricity. 4) Give a reason why Al is preferred to Mg for making cooking pans. Aluminum is preferred over magnesium for making cooking pans primarily due to its superior corrosion resistance. Aluminum forms a thin, tough, and impermeable layer of aluminum oxide (Al₂O₃) on its surface when exposed to air, which protects the underlying metal from further corrosion, especially from acids found in food. Magnesium is more reactive and can corrode more easily, particularly in the presence of water or acids at cooking temperatures. Send me the next one 📸

When 50cm³ of 2M HCl was neutralised by an equal volume of 2M NaOH, it initially rose to a minimum of 33.7°C. What is the molar enthalpy of neutralisation of NaOH?

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When 50cm³ of 2M HCl was neutralised by an equal volume of 2M NaOH, it initially rose to a minimum of 33.7°C. What is the molar enthalpy of neutralisation of NaOH?

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