How much heat (in kilojoules) is evolved or absorbed in the reaction of 2.65 g of Na with H2O?
2Na+2H2O ---> 2NaOH + 2H2 Delta H= -368.4
Is that 368.4 J/mole of reactant or 368.4 J/reaction shown? It makes a difference? Also, you have no units on 368.4; I assume that is joules.
How many moles Na do you have?
2.65 g/atomic mass Na = moles Na.
If 368.4 J heat is released for the reaction as shown, then set up a proportion.
12
The chinese
To determine the amount of heat evolved or absorbed in the given reaction, we need to use the provided enthalpy change (ΔH) value and the amount of substance involved (in this case, the mass of sodium, which is 2.65 g).
First, we need to calculate the number of moles of sodium (Na) involved in the reaction. We can do this by dividing the given mass by the molar mass of sodium (22.99 g/mol):
Number of moles of Na = mass of Na / molar mass of Na
= 2.65 g / 22.99 g/mol
Next, we need to use stoichiometry to determine the amount of heat evolved or absorbed when the given number of moles of sodium reacts. From the balanced chemical equation, we can see that the molar ratio between sodium (Na) and the enthalpy change (ΔH) is 2:1. Therefore, we can set up the following ratio:
ΔH / 2 moles of Na = -368.4 kJ / 2
Now, we can use the ratio to calculate the amount of heat evolved or absorbed when the given number of moles of sodium reacts:
Heat evolved or absorbed = (Number of moles of Na) × (ΔH / 2 moles of Na)
Substituting the values:
Heat evolved or absorbed = (2.65 g / 22.99 g/mol) × (-368.4 kJ / 2)
= (0.115 moles) × (-368.4 kJ / 2)
= -21.135 kJ
Therefore, the amount of heat evolved or absorbed in the reaction of 2.65 g of Na with H2O is approximately -21.135 kJ. The negative sign indicates that the reaction is exothermic (heat is evolved).