How much heat (in kilocalories) is evolved or absorbed in the reaction of 1.60 g of Na with H2O?
2Na(s)+2H2O(l)→2NaOH(aq)+H2(g), ΔH = -88.0 kcal (-368 kJ)
To determine the amount of heat evolved or absorbed in the reaction, we need to use the concept of stoichiometry and the given information.
Given:
- Mass of Na = 1.60 g
- Balanced equation: 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
- Enthalpy change (ΔH) = -88.0 kcal (-368 kJ)
First, we need to calculate the number of moles of Na that react. To do this, we use the molar mass of Na.
Molar mass of Na = 22.99 g/mol
Number of moles of Na = Mass of Na / Molar mass of Na
= 1.60 g / 22.99 g/mol
≈ 0.0696 mol
From the balanced equation, we can see that 2 moles of Na react to produce -88.0 kcal of energy.
So, for 0.0696 mol of Na, the amount of heat evolved or absorbed can be calculated as follows:
Heat evolved or absorbed = (ΔH / 2 moles) × number of moles of Na
= (-88.0 kcal / 2 mol) × 0.0696 mol
= -3.85 kcal
Therefore, approximately 3.85 kcal of heat is evolved or absorbed in the reaction of 1.60 g of Na with H2O.