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
Rus_ich [418]
3 years ago
13

[Standard Enthalpy of Formation]

Chemistry
2 answers:
Pie3 years ago
7 0
This is the answer using hess’ law. you need to make the 3 equations equal the final one

SpyIntel [72]3 years ago
3 0

Answer:

5. ΔH = 238.7 kJ; 6 ΔH, = -1504.6 kJ

Step-by-step explanation:

Question 5:

We have three equations:  

(I)  CH₃OH + ³/₂O₂ ⟶ CO₂ + 2H₂O;  ΔH = -726.4 kJ

(II)  C + O₂ ⟶ CO₂;                              ΔH = -393.5 kJ

(III) H₂ + ½O₂ ⟶ H₂O;                         ΔH = -285.8 kJ

From these, we must devise the target equation:  

(IV) C + 2H₂ + ½ O₂ → CH₃OH; ΔH = ?  

The target equation has 1C on the left, so you rewrite Equation (II)..  

(V) C + O₂ ⟶ CO₂;                               ΔH = -393.5 kJ

Equation (V) has 1CO₂ on the right, and that is not in the target equation.  

You need an equation with ½O₂ on the left, so you <em>reverse Equation (I).  </em>

When you reverse an equation, you r<em>everse the sign</em> of its ΔH.  

(VI) CO₂ + 2H₂O ⟶ CH₃OH + ³/₂O₂;  ΔH = 726.4 kJ

Equation (VI) has 2H₂O on the left, and that is not in the target equation.

You need an equation with 2H₂O on the right. Double Equation (III).

When you <u>double an equation, you double its ΔH</u>.  

(VII) 2H₂ + O₂ ⟶ 2H₂O;                        ΔH = -571.6 kJ

Now, you add equations (V), (VI), and (VII), <em>cancelling species</em> that appear <em>on opposite sides</em> of the reaction arrows.

When you add equations, you add their ΔH values.

We get the target equation (IV)  

(V)   C + O₂ ⟶ CO₂;                              ΔH = -393.5 kJ

(VI)  CO₂ + 2H₂O ⟶ CH₃OH + ³/₂O₂ ;  ΔH =  726.4 kJ

<u>(VII</u><u>) 2H₂ + O₂ ⟶ 2H₂O;          </u>              <u>ΔH = -571.6 kJ </u>

(IV)  C + 2H₂ + ½ O₂ → CH₃OH;             ΔH = -238.7 kJ  

Question 6

We have three equations:  

(I) Mg + ½O₂ → MgO;  ΔH = -601.7 kJ

(II) Mg + S ⟶ MgS;      ΔH = -598.0 kJ

(III) S + O₂ ⟶ SO₂;       ΔH = -296.8 kJ

From these, we must devise the target equation:  

(IV) 3Mg + SO₂ → MgS + 2MgO; ΔH = ?  

The target equation has 1SO₂ on the left, so you reverse Equation(III).

(V) SO₂ ⟶ S + O₂;         ΔH = 296.8 kJ

Equation (V) has 1S on the right, and that is not in the target equation.  

You need an equation with 1S on the left, so you rewrite Equation (II).  

(VI) Mg + S ⟶ MgS;        ΔH = -598.0 kJ

Equation (V) has 1O₂ on the right, and that is not in the target equation.

You need an equation with 1O₂ on the left. Double Equation (I).

(VII) 2Mg + O₂⟶ 2MgO ;  ΔH = -1203.4 kJ  

Now, you add equations (V), (VI), and (VII), cancelling species that appear on opposite sides of the reaction arrows.

We get the target equation (IV)  

(V)   SO₂ ⟶ S + O₂;                    ΔH =    296.8 kJ

(VI)   Mg + S ⟶ MgS;                  ΔH = -  598.0 kJ

<u>(VII)</u><u> 2Mg + O₂ ⟶ 2MgO;          </u>  <u>ΔH = -1203.4 kJ </u>

(IV)  3Mg + SO₂ → MgS + 2MgO; ΔH = -1504.6 kJ

You might be interested in
Is NaCl an ionic or covalent compound?<br>Explain.​
diamong [38]
NaCl is an ionic compound because Chlorine is a nonmetal and Sodium is a metal (Alkali Metal Group)
5 0
3 years ago
True or False. If a fire destroyed all of the grass in a grassland, this would NOT affect the biodiversity of this ecosystem.
Andrews [41]

Answer:

This is false

5 0
3 years ago
Read 2 more answers
Which is a NOT a freshwater source on Earth?
cluponka [151]

Answer:

B the atmosphere it's not on earth and I'm pretty sure  the atmosphere doesn't have water in

Explanation:

7 0
2 years ago
How many milliliters of 0.125 M FeCl3 are needed to react with an excess of Na2S to produce 3.75 g of Fe2S3 if the percent yield
Katyanochek1 [597]

Answer:

0.912 mL

Explanation:

3 Na2S(aq) + 2 FeCl3(aq) → Fe2S3(s) + 6 NaCl(aq)

FeCl3 is the limiting reactant.

Number of moles of iron III sulphide produced= 3.75g/87.92 g/mol = 0.043 moles

Hence actual yield of Iron III sulphide = 0.043 moles

Theoretical yield of Iron III sulphide = actual yield ×100%/ %yield

Theoretical yield of iron III sulphide= 0.043 ×100/75 = 0.057 moles of Iron III sulphide

From the reaction equation,

2moles of iron III chloride produced 1 mole of iron III sulphide

x moles of iron III chloride, will produce 0.057 of iron III sulphide

x= 2× 0.057= 0.114 moles of iron III chloride

But

Volume= number of moles/ concentration

Volume= 0.114/0.125

Volume= 0.912 mL

4 0
3 years ago
Using current genetic engineering techniques can provide potential benefits for parents, including
Black_prince [1.1K]

Answer:

conceiving a child who is a bone marrow match to a living child.

Explanation:

5 0
3 years ago
Read 2 more answers
Other questions:
  • Your friend makes the statement that, “Water boils at a higher temperature than ethanol.” To which step of the scientific method
    9·1 answer
  • Which of the following are considered pure substances?
    11·2 answers
  • In a controlled scientific experiment,a scientist
    5·2 answers
  • In a chemical reaction the physical states of each chemical species is denoted by a state symbol. Each state is represented by a
    7·1 answer
  • a person drinks eight glasses of water each day, if each glass contains 300mL how many liters of water does a person drink in a
    15·1 answer
  • Question 2
    7·1 answer
  • Which of the following polyatomic ions has a 3- ionic charge?
    11·1 answer
  • A 25.0 mL sample of 0.100 M pyridine (Kb for pyridine is 1.7 ✕ 10-9) is titrated with 0.100 M HCl solution. Calculate the pH aft
    6·1 answer
  • Would you expect manganese(II) oxide, MnO, to react more readily with HF(aq) or NaOH(aq)?
    5·1 answer
  • What are periods on the periodic table? How many are there?
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!