The weather instruments: rain gauge can measure the amount of snow fall True or false

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

mina [271]

Answer: The amount of energy released per gram of $B_5H_9$ is -71.92 kJ

Explanation:

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

What does a plant produce during photosynthesis? A. Oxygen and glucose B. Carbohydrates and carbon C. Carbon, oxygen, and hydrog

Nataliya [291]

Answer:

im pretty sure b

Explanation:

3 0

4 years ago

How many molecules are in 5.00 grams of NH3

leva [86]

Answer:

0.293590565643325

8 0

4 years ago

How many milliliters of water will be created from a combustion reaction with 9.32×10 22nd power of ethanol molecules. Assume de

PolarNik [594]

Answer:

8.38 mL

Explanation:

1- The combustion reaction of ethanol (C2H5OH) in the presence of oxygen (O2) has as reaction products carbon dioxide (CO2) and water (H2O), the equation equaled is:

C2H5OH (l) + 3 O2 (g) CO2 2 CO2 (g) + 3 H2O (l)

2- By establishing the stoichiometric relationship between ethanol and water, you can calculate the number of molecules that will be created from the initial amount of alcohol molecules:

6,022x10 23 molecules of C2H5OH (1 mol) ___ 3 x 6,022x10 23 molecules of H2O (3 moles)

9.32x10 22 C2H5OH molecules _____ X = 2.80x10 23 H2O molecules

Calculation:

9.32x10 22 x (3 x 6.022x10 23) / 6.022x10 23 = 2.80x10 23 H2O molecules

3- Once the number of water molecules formed is obtained, with the molar mass the mass can be determined:

6.022x10 23 H2O molecules _____ 18.02 g

2.80x10 23 molecules of H2O _____ X = 8.38 g of H2O

Calculation:

2.80x10 23 x 18.02 g / 6.022x1023 = 8.38 g of H2O

4- Finally, having the density of water, you can calculate the volume that formed:

d = m / V --> V = m / d

V = 8.38 g / 1.00 mL = 8.38 mL

The answer is that 8.38 mL of water is formed

5 0

3 years ago

How many moles in 2 h2o molecules

alexandr1967 [171]

Answer:

2 molecules of water represents 3.32 x 10^-24 moles of water.

Explanation:

To find the solution to this problem, you have to use the concept of Avogadro´s number, that is in 1 mol of any element o compound there are 6.022 x 10^23 molecules. Then,

1 mol H2O ------------- 6.022 x 10^23 molecules

x= 3.32 x 10^-24 ---- 2 molecules.

2 molecules of water represents 3.32 x 10^-24 moles of water.

5 0

3 years ago