How many kilojoules of heat are released when 54.9 g of manganese is burned to form Mn ₃ O ₄ (s)? Given that Δ H for the reaction is − 25.3 kJ/g.

Question

Quizplus · Accepted Answer

First, we need to calculate the amount of moles of manganese burned.

manganese (Mn) = 54.9 g

molar mass of Mn = 54.9 g/mol

moles of Mn = 54.9 g / 54.9 g/mol = 1 mol

Now we can use the given ΔH and the stoichiometry of the reaction to calculate the heat released.

ΔH = -25.3 kJ/g

moles of Mn = 1 mol

So, the heat released = -25.3 kJ/g x 1 mol x 4 mol = -101.2 kJ

However, the question asks for the heat released in kilojoules, so we need to convert the answer to kJ.

-101.2 kJ x (1 kJ/1000 J) = -0.1012 kJ

But we need the answer in positive kJ since the question asks for the amount of heat released (not absorbed).

So, the final answer is:

Answer: E

The amount of heat released when 54.9 g of manganese is burned is 1389 kJ.

How Many Kilojoules of Heat Are Released When 54