1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
zmey [24]
3 years ago
15

Using enthalpies of formation, calculate H.

Chemistry
1 answer:
Korvikt [17]3 years ago
3 0

ΔH° = -851.5 kJ/mol given that

\begin{array}{cc}\textbf{Species}&{\bf {\Delta H_f\textdegree{}}}\\ \text{Fe}_2\text{O}_3\;(s) & -824.2\;\text{kJ}\cdot\text{mol}^{-1}\\\text{Al}_2\text{O}_3\;(s) & -1675.7\;\text{kJ}\cdot\text{mol}^{-1}\end{array}

(Source: Chemistry Libretexts.)

<h3>Explanation</h3>

Refer to a thermodynamic data table for the standard enthalpy of formation for each species.

Don't be alerted if the data for Al (s) and Fe (s) are missing. Why?

  • The standard enthalpy of formation of a substance measures the ΔH required to form each mole of it from the most stable allotrope of its elements under STP.
  • Both Al (s) and Fe (s) are already the most stable form of their element under STP (note that the state symbol matters.) There's no need to form them again.

As a result, \Delta H_f\textdegree{} = 0 for both Al (s) and Fe (s).

\displaystyle \Delta H_{\text{rxn}}\textdegree{} = \text{Sum of }\Delta H\text{ for all }\textbf{Product} - \text{Sum of }\Delta H\text{ for all }\textbf{Reactant}}\\\phantom{\Delta H_{\text{rxn}}\textdegree{}} = (1\times \Delta H_f\textdegree{}(\text{Al}_2\text{O}_3\;(s)) + 1\times \Delta H_f\textdegree{}(\text{Al}\;(s)) \\ \phantom{\Delta H_{\text{rxn}}\textdegree{}=}-(1\times \Delta H_f\textdegree{}(\text{Fe}_2\text{O}_3\;(s)) + 1\times\Delta H_f\textdegree{}(\text{Fe}\;(s))

\Delta H_{\text{rxn}}\textdegree{}} = (1 \times (-1675.7)) - (1\times(-824.2)) = -851.5\;\text{kJ}\cdot\text{mol}^{-1}.

The number "1" here emphasizes that in case there are more than one mole of any species in one mole of the reaction, it will be necessary to multiply the \Delta H_f\textdegree{} of that species with its coefficient in the equation.

You might be interested in
Urea, (NH2)2CO, is a product of metabolism of proteins. An aqueous solution is 37.2% urea by mass and has a density of 1.032 g/m
Feliz [49]

Answer:

The molarity of urea in this solution is 6.39 M.

Explanation:

Molarity (M) is <em>the number of moles of solute in 1 L of solution</em>;  that is

molarity = moles of solute ÷ liters of solution

To calculate the molality, we need to know the number of moles of urea and the volume of solution in liters. We assume 100 grams of solution.

Our first step is to calculate the moles of urea in 100 grams of the solution,

using the molar mass a conversion factor. The total moles of 100g of a 37.2 percent by mass solution is

60.06 g/mol ÷ 37.2 g = 0.619 mol

Now we need to calculate the volume of 100 grams of solution, and we use density as a conversion factor.

1.032 g/mL ÷ 100 g = 96.9 mL

This solution contains 0.619 moles of urea in 96.9 mL of solution. To express it in molarity, we need to calculate the moles present in 1000 mL (1 L) of the solution.

0.619 mol/96.9 mL × 1000 mL= 6.39 M

Therefore, the molarity of the solution is 6.39 M.

4 0
3 years ago
Check my answer plz!! 100 points. Tell me if they are wrong! 1. You have three elements, A, B, and C, with the following electro
Artyom0805 [142]

look good w small changes below:

Answer:  


AB is an ionic compound. The electronegativity difference between A and B is greater.  


AC is an ionic compound. The electronegativity difference between A and C is greater.  


BC is a covalent compound because the electronegativity difference between C and B is small.


everything else look good!

6 0
3 years ago
Read 2 more answers
Why steam distillation is usefull for thermally un stable compounds​
g100num [7]

The advantage of steam distillation over simple distillation is that the lower boiling point reduces decomposition of temperature -sensitive compounds.

4 0
3 years ago
Study the Lewis dot diagram for nitrogen. Explain what is correct and what is incorrect about the diagram. Use details to suppor
Verdich [7]

Answer:

The Lewis dot diagram is supposed to have dots on each side. What's incorrect is that there isn't a dot on the bottom, only the left and right side and the top. What's correct about this is that there are 5 outer valence electrons, and they correctly put 5 dots, even though they're in the wrong place.

Explanation:

4 0
3 years ago
ASAP!!!!!!!!!!!!
dlinn [17]
<span>a. Tall prarie grass burns after being struck by lightning.</span>
6 0
3 years ago
Other questions:
  • If the sentence is true, write true. If the sentence is false , replace the underlined word to make the sentence true.
    11·1 answer
  • The process by which molecules of water vapor in the air become liquid water answers
    5·1 answer
  • 5) How do you describe a person who likes<br>inventing stories?<br>Plz Help ;_; :v​
    9·1 answer
  • Light strikes a beautiful white perch under water. This light is reflected back to your eyes allowing you to see the fish. As th
    6·1 answer
  • For carbon monoxide poisoning, the treatment is administration of oxygen at high pressure. This increases the amount of oxyhemog
    7·2 answers
  • 1. How does hydrogen bonding affect water molecules?
    12·1 answer
  • I need an Honest answer.. and I also didnt know where to post this question under.
    9·2 answers
  • First to help me with these 4 gets brainless HURRYTTT UPPPPP
    10·2 answers
  • Plz help i will give 32 points is it weather or climate i need help asap and i will give brainly
    11·2 answers
  • POS MOLECULES SPEED UP WHEN ENERGY IS CREATED AND SLOW DOWN WHEN ENERGY IS DESTROYED True False? explain why​
    7·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!