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2 years ago

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Chemistry

2 answers:

FrozenT [24]2 years ago

6 0

what is your question?

velikii [3]2 years ago

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Whats your question

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Pentaborane-9, B5H9, is a colorless, highly reactive liquid that will burst into flame when exposed to oxygen. The reaction is 2

mina [271]

<u>Answer:</u> The amount of energy released per gram of $B_5H_9$ is -71.92 kJ

<u>Explanation:</u>

For the given chemical reaction:

$2B_5H_9(l)+12O_2(g)\rightarrow 5B_2O_3(s)+9H_2O(l)$

The equation used to calculate enthalpy change is of a reaction is:

$\Delta H^o_{rxn}=\sum [n\times \Delta H^o_f_{(product)}]-\sum [n\times \Delta H^o_f_{(reactant)}]$

The equation for the enthalpy change of the above reaction is:

$\Delta H^o_{rxn}=[(5\times \Delta H^o_f_{(B_2O_3(s))})+(9\times \Delta H^o_f_{(H_2O(l))})]-[(2\times \Delta H^o_f_{(B_5H_9(l))})+(12\times \Delta H^o_f_{(O_2(g))})]$

Taking the standard enthalpy of formation:

$\Delta H^o_f_{(B_2O_3(s))}=-1271.94kJ/mol\\\Delta H^o_f_{(H_2O(l))}=-285.83kJ/mol\\\Delta H^o_f_{(B_5H_9(l))}=73.2kJ/mol\\\Delta H^o_f_{(O_2(g))}=0kJ/mol$

Putting values in above equation, we get:

$\Delta H^o_{rxn}=[(5\times (1271.94))+(9\times (-285.83))]-[(2\times (73.2))+(12\times (0))]\\\\\Delta H^o_{rxn}=-9078.57kJ$

We know that:

Molar mass of pentaborane -9 = 63.12 g/mol

By Stoichiometry of the reaction:

If 2 moles of $B_5H_9$ produces -9078.57 kJ of energy.

Or,

If $(2\times 63.12)g$ of $B_5H_9$ produces -9078.57 kJ of energy

Then, 1 gram of $B_5H_9$ will produce = $\frac{-9078.57kJ}{(2\times 63.12)}\times 1g=-71.92kJ$ of energy.

Hence, the amount of energy released per gram of $B_5H_9$ is -71.92 kJ

8 0

3 years ago

HELP ME PLZ!!!!

Degger [83]

The answers is B that’s your answer

4 0

2 years ago

Carbon, hydrogen, and oxygen are always found in what type of molecule?

Snowcat [4.5K]

Carbohydrates, proteins, lipids, and Nucleic Acids.

3 0

3 years ago

g If a sample of 50 mL of ethyl benzene (bp = 136 C) was contaminated with 10 mL of ethyl acetate (bp = 77 C) what effect would

PolarNik [594]

Answer:

melting point will be higher than that of pure ethyl acetate

Explanation:

6 0

2 years ago

What is the final volume (l) of a 10.0 l system that has the pressure quartered?

mihalych1998 [28]

According to Boyle's Law, P1V1 = P2V2

where P1 and V1 are initial pressure and volume respectively. P2 and V2 are final pressure and volume receptively.

Given: P2 = 4 P1 and V1 = 10.0l

∴ V2 = 2.5 l

Answer: Final volume of system is 2.5 l

5 0

2 years ago