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Pentaborane- $9, \mathrm{B}_{5} \mathrm{H}_{9},$ is a colorless, highly reactive liquid that will burst into flame when exposed to oxygen. The reaction is $$2 \mathrm{B}_{5} \mathrm{H}_{9}(l)+12 \mathrm{O}_{2}(g) \longrightarrow 5 \mathrm{B}_{2} \mathrm{O}_{3}(s)+9 \mathrm{H}_{2} \mathrm{O}(l)$$ Calculate the kilojoules of heat released per gram of the compound reacted with oxygen. The standard enthalpy of formation of $\mathrm{B}_{5} \mathrm{H}_{9}$ is $73.2 \mathrm{kJ} / \mathrm{mol}.$

$71.7 k . J$ heat released per gram

Chemistry 101

Chapter 6

Thermochemistry

Drexel University

Brown University

University of Toronto

Lectures

05:27

In chemistry, a chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Both reactants and products are involved in the chemical reactions.

06:42

In chemistry, energy is what is required to bring about a chemical reaction. The total energy of a system is the sum of the potential energy of its constituent particles and the kinetic energy of these particles. Chemical energy, also called bond energy, is the potential energy stored in the chemical bonds of a substance. Chemical energy is released when a bond is broken during chemical reactions.

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Pentaborane-9 ( $\mathrm{B…

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So for this problem, we're supposed to find the killer. Jill's Laffite, released per gram of the compound of a program of compound reacted with oxygen. The given reaction is the following. So the first step in solving this problem is finding the Delta h of this entire reaction. And from there we can find the final answer. So Delta h of this entire reaction can be expressed as the nine times the heat information of age to plus five times the heat of formation of B two or three minus the heat information of the reactant. But for oxygen, you know that that zero, because it's an element. So the only thing we need to subtract is two times the heat information of be five h nine. And so when you look up the heats information for each of those things, we could then plug those values into this equation. So for the heat information of water negative 285 0.8 killer jewels promote The heat of formation of B 203 is negative 1263.5 kilograms per mole. And finally, the heat of reaction of the heat of formation of beat of be five h nine is 73.2 killer joules per mole. As given in the problem. When you put all of that into the calculator, you will see that this yields negative 9000 and 36 0.1 killer jewels for more. Now the problem here is that this isn't the final answer because it isn't in terms of the grams of oxygen that is reacted. And so we need to express it in terms of grants. So we know that negative 9000 and 36 killed Jules are released for every two moles of be five each nine. We simply then divide by the molar mass of be five h nine to get it in terms of grams and the molar mass of be five h night happens to be 63 grams and let me plug it in. You get the final answer is negative 71.7 killer jewels per gram of be five h nine, and that is the final answer

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