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
sesenic [268]
3 years ago
10

Calculate Delta H in KJ for the following reactions using heats of formation:

Chemistry
1 answer:
lozanna [386]3 years ago
6 0

Answer:

<h3>(a)</h3>

\Delta H\textdegree = -2856.8\;\text{kJ} per mole reaction.

<h3>(b)</h3>

\Delta H\textdegree = -22.3\;\text{kJ} per mole reaction.

Explanation:

What is the standard enthalpy of formation \Delta H_f\textdegree{} of a substance? \Delta H_f\textdegree{} the enthalpy change when one mole of the substance is formed from the most stable allotrope of its elements under standard conditions.

Naturally, \Delta H_f\textdegree{} = 0 for the most stable allotrope of each element under standard conditions. For example, oxygen \text{O}_2 (not ozone \text{O}_3) is the most stable allotrope of oxygen. Also, under STP \text{O}_2  is a gas. Forming \text{O}_2\;(g) from itself does not involve any chemical or physical change. As a result, \Delta H_f\textdegree{} = 0 for \text{O}_2\;(g).

Look up standard enthalpy of formation \Delta H_f\textdegree{} data for the rest of the species. In case one or more values are not available from your school, here are the published ones. Note the state symbols of the compounds (water/steam \text{H}_2\text{O} in particular) and the sign of the enthalpy changes.

  • \text{C}_2\text{H}_6\;(g): -84.0\;\text{kJ}\cdot\text{mol}^{-1};
  • \text{CO}_2\;(g): -393.5\;\text{kJ}\cdot\text{mol}^{-1};
  • \text{H}_2\text{O}\;{\bf (g)}: -241.8\;\text{kJ}\cdot\text{mol}^{-1};
  • \text{PbO}\;(s): -217.9\;\text{kJ}\cdot\text{mol}^{-1};
  • \text{PbO}_2\;(s): -276.6\;\text{kJ}\cdot\text{mol}^{-1};
  • \text{Pb}_3\text{O}_4\;(s): -734.7\;\text{kJ}\cdot\text{mol}^{-1}

How to calculate the enthalpy change of a reaction \Delta H_\text{rxn} (or simply \Delta H from enthalpies of formation?

  • Multiply the enthalpy of formation of each product by its coefficient in the equation.
  • Find the sum of these values. Label the sum \Sigma (n\cdot \Delta_f(\text{Reactants})) to show that this value takes the coefficients into account.
  • Multiply the enthalpy of formation of each reactant by its coefficient in the equation.
  • Find the sum of these values. Label the sum \Sigma (n\cdot \Delta_f(\text{Products})) to show that this value takes the coefficient into account.
  • Change = Final - Initial. So is the case with enthalpy changes. \Delta H_\text{rxn} = \Sigma (n\cdot \Delta_f(\textbf{Products})) - \Sigma (n\cdot \Delta_f(\textbf{Reactants})).

For the first reaction:

  • \Sigma (n\cdot \Delta_f(\text{Reactants})) = 4\times (-393.5) + 6\times (-241.8) = -3024.8\;\text{kJ}\cdot\text{mol}^{-1};
  • \Sigma (n\cdot \Delta_f(\text{Products})) = 2\times (-84.0) + 7\times 0 = -168.0\;\text{kJ}\cdot\text{mol}^{-1};
  • \begin{aligned}\Delta H_\text{rxn} &= \Sigma (n\cdot \Delta_f(\textbf{Products})) - \Sigma (n\cdot \Delta_f(\textbf{Reactants}))\\ &= (-3024.8\;\text{kJ}\cdot\text{mol}^{-1}) - (-168.0\;\text{kJ}\cdot\text{mol}^{-1})\\ &= -2856.8\;\text{kJ}\cdot\text{mol}^{-1} \end{aligned}.

Try these steps for the second reaction:

\Delta H_\text{rxn} = -22.3\;\text{kJ}\cdot\text{mol}^{-1}.

You might be interested in
What ingredients are needed to turn the cake mix into cake batter​
svp [43]

Answer:

Ingredients

2 ⅓ cups all-purpose flour.

1 tablespoon baking powder.

¾ teaspoon salt.

1 ½ cups white sugar.

½ cup shortening.

2 eggs.

1 cup milk.

1 teaspoon vanilla extract.

Explanation:

4 0
2 years ago
HELP ME PLEASE!!!!
liq [111]

Answer:

1.D

2.A

3.C

4.A

Explanation:

6 0
3 years ago
Read 2 more answers
Will bromine react with sodium and why?
Archy [21]

<span><span>When you write down the electronic configuration of bromine and sodium, you get this

Na:
Br: </span></span>

<span><span />So here we the know the valence electrons for each;</span>

<span><span>Na:  (2e)
Br:  (7e, you don't count for the d orbitals)

Then, once you know this, you can deduce how many bonds each can do and you discover that bromine can do one bond since he has one electron missing in his p orbital, but that weirdly, since the s orbital of sodium is full and thus, should not make any bond.

However, it is possible for sodium to come in an excited state in wich he will have sent one of its electrons on an higher shell to have this valence configuration:</span></span>

<span><span /></span><span><span>

</span>where here now it has two lonely valence electrons, one on the s and the other on the p, so that it can do a total of two bonds.</span><span>That's why bromine and sodium can form </span>

<span>
</span>

4 0
3 years ago
I need help please! I will mark brainliest
Fittoniya [83]

Answer: I think it's C

Explanation: I hope this helps (Sorry if it doesn't)

8 0
1 year ago
A wetland being drained so a housing development can be built is an example of ____________.
Reil [10]

Answer:

a now give me the points

Explanation:

5 0
2 years ago
Other questions:
  • (a) How much negative charge is on each oxygen of the carbonate ion?
    5·1 answer
  • You evaporate all of the water from 100 mL of NaCl solution and obtain 11.3 grams of NaCl. What was the molarity of the NaCl sol
    15·1 answer
  • How many grams of CO2 are in 11 mol of the compound?
    12·1 answer
  • Please...help!
    10·2 answers
  • PLZ HELP! WILL GIVE BRAINLIEST, 5 STARS, AND A THANKS!!
    8·2 answers
  • Can I have Help? please
    13·2 answers
  • A sample of a compound used to polish dentures and as a nutrient and dietary supplement is analyzed and found to contain 9.0231
    11·1 answer
  • What do the forms of the highlighted limbs in the illustration tell you about their functions in each animal?
    9·2 answers
  • What makes a good scientific question??? <br> Plsss help! I will give brainliest! :)
    14·2 answers
  • Use the chemical equation and the bond diagram to answer the question.
    15·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!