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
uranmaximum [27]
3 years ago
8

Must show work for questions. Please also explain, I don't understand.

Chemistry
1 answer:
prisoha [69]3 years ago
3 0

Answer:

11. 227 kJ·mol⁻¹; 12. 587 kJ

Step-by-step explanation:

11. Calculate ΔH°f

The formula for calculating the enthalpy change of a reaction by using the enthalpies of formation of reactants and products is

ΔH°r = ΣmΔH°f(products) - ΣnΔH°f(reactants)

                        2C₂H₂ + 5O₂ ⟶ 4CO₂ + 2H₂O; ΔH°c = -1299 kJ·mol⁻¹

ΔH°f/kJ·mol⁻¹:      2x         0          -393     -286

2(-1299) = 4(-393) + 2(-286) - 2x

  -2598 = -1572 - 572 - 2x

  -2598 = -2144 -2x

    -454 = -2x

         x = 227 kJ·mol⁻¹

ΔH°f for acetylene is 227 kJ·mol⁻¹

12. Hess's Law

Warning: It is almost impossible to solve a problem like this by trial and error. You must have a strategy beforehand.

We have five equations:

(I)     Ca + 2C ⟶ CaC₂;                    ΔH =    -62.8   kJ

(II)   Ca + ½O₂ ⟶ CaO;                   ΔH =   -635.5  kJ

(III) CaO + H₂O ⟶ Ca(OH)₂;           ΔH =   -653.1   kJ

(IV) C₂H₂ + ⁵/₂O₂ ⟶ 2CO₂ + H₂O;  ΔH = -1300     kJ

(V)  C + O₂ ⟶ CO₂;                         ΔH =   -393.51 kJ

From these, we must devise the target equation:  

(VI) CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂;  ΔH = ?  

Here comes the strategy. Remember, you can use each of the given equations only once.  

Start with the target equation. It has CaC₂ on the left, so you need an equation containing CaC₂ on the left.  

Reverse Equation (I). When you reverse an equation, you <em>change the sign of its ΔH</em>.

(VII) CaC₂ ⟶ Ca + 2C; ΔH = 62.8   kJ

Equation (VII) has Ca on the right, and that is not in the target. You need an equation with Ca on the left to cancel it. Add Equation (II)

(VIII) Ca + O₂ ⟶ CaO; ΔH = -1271.0 kJ

Equation (VII) also has 2C on the right, and there is no C in the target. We need an equation with 2C on the left to cancel it.

Double Equation (V). When you double an equation, you double its ΔH.

(IX) 2C + 2O₂ ⟶ 2CO₂; ΔH = -587.02 kJ

Now, we must eliminate the CaO from Equation (VII). Add Equation (III).

(X) CaO + H₂O ⟶ Ca(OH)₂; ΔH = -653.1 kJ

Equation (VIII) has 2CO₂ on the right. You need an equation with 2CO₂ on the left.

Reverse Equation (IV).

(XI) 2CO₂ +H₂O ⟶ C₂H₂ + ⁵/₂O₂ ; ΔH = 2600  kJ

Now, we add all five equations,  cancelling substances that appear on both sides of the reaction arrow. All the formulas in italics have been cancelled

(VII)  CaC₂ ⟶ <em>Ca</em> + <em>2C</em>;                           ΔH =   62.8   kJ

(VIII) <em>Ca</em> + <em>½O₂</em> ⟶ <em>CaO</em>;                         ΔH = -635.5   kJ

(IX)   <em>2C </em>+ <em>2O₂</em> ⟶ <em>2CO₂</em>;                        ΔH = -787.02 kJ

(X)    <em>CaO</em> + H₂O ⟶ Ca(OH)₂;                ΔH = -653.1    kJ

<u>(XI)   </u><em><u>2CO₂</u></em><u> + </u><u>H₂O</u><u> ⟶ </u><u>C₂H₂</u><u> + ⁵</u><em><u>/₂O₂  </u></em><u>   </u> ; ΔH = <u>2600     kJ </u>

(VI)   CaC₂ + 2H₂O → Ca(OH)₂ + C₂H₂;  ΔH =    587     kJ

ΔH = 587 kJ

You might be interested in
How do scientists use radioactive decay to date fossils and artifacts
liubo4ka [24]

Answer: Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods. This uses radioactive minerals that occur in rocks and fossils almost like a geological clock. ... These isotopes break down at a constant rate over time through radioactive decay.

8 0
3 years ago
Ms. Clark added a spoonful of baking soda and then poured a little vinegar into the cup. We observed fizzing and bubbling. Based
leva [86]

Answer:

we know that it was the vinegar and baking soda because gas had been created, the gas was held within the bubbles. the gas that was created was called Carbon Dioxide or CO2

7 0
3 years ago
Which statement is true about a pseudoscientific?​
Alex17521 [72]

Answer:

Wereare they answer choices

Explanation:

7 0
3 years ago
Read 2 more answers
Fission and Fusion of Atomic Nuclei:
bogdanovich [222]

Answer:

C B A D

Explanation:

6 0
3 years ago
A sample of solid sodium hydroxide, weighing 13.20 grams is dissolved in deionized water to make a solution. What volume in mL o
Andreas93 [3]
<h3>Answer:</h3>

2.809 L of H₂SO₄

<h3>Explanation:</h3>

Concept tested: Moles and Molarity

In this case we are give;

Mass of solid sodium hydroxide as 13.20 g

Molarity of H₂SO₄ as 0.235 M

We are required to determine the volume of H₂SO₄ required

<h3>First: We need to write the balanced equation for the reaction.</h3>
  • The reaction between NaOH and H₂SO₄ is a neutralization reaction.
  • The balanced equation for the reaction is;

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

<h3>Second: We calculate the umber of moles of NaOH used </h3>
  • Number of moles = Mass ÷ Molar mass
  • Molar mass of NaOH is 40.0 g/mol
  • Therefore;

Moles of NaOH = 13.20 g ÷ 40.0 g/mol

                          = 0.33 moles

<h3>Third: Determine the number of moles of the acid, H₂SO₄</h3>
  • From the equation, 2 moles of NaOH reacts with 1 mole of H₂SO₄
  • Therefore, the mole ratio of NaOH: H₂SO₄ is 2 : 1.
  • Thus, Moles of H₂SO₄ = moles of NaOH × 2

                                    = 0.33 moles × 2

                                   = 0.66 moles of H₂SO₄

<h3>Fourth: Determine the Volume of the acid, H₂SO₄ used</h3>
  • When given the molarity of an acid and the number of moles we can calculate the volume of the acid.
  • That is; Volume = Number of moles ÷ Molarity

In this case;

Volume of the acid = 0.66 moles ÷ 0.235 M

                                = 2.809 L

Therefore, the volume of the acid required to neutralize the base,NaOH is 2.809 L.

7 0
3 years ago
Other questions:
  • What is the simplest formula for Sr4S4?
    12·1 answer
  • A Is an ecosystem that is covered with water for at least part of the year
    11·1 answer
  • Alcohol and water have different boiling points. Which method would you use to separate them
    5·2 answers
  • When you are in a relationship with a male but you are bi and they find out(and act a little weird) what do you do? I just need
    10·2 answers
  • Which of these characteristics differentiate electrons from protons and neutrons
    15·1 answer
  • Which particle has no charge
    12·1 answer
  • Write ground-state electron configurations for these ions, which play important roles in biochemical processes in our bodies. (U
    11·1 answer
  • Match the following properties with the type of property they are (chemical or physical) or the type of change the substance is
    6·1 answer
  • Background research about water purification and filtration!!!
    9·1 answer
  • MARKING BRAINLEIST + 20 POINTS Explain why energy must be added to a solid to cause it to melt?
    12·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!