Chemistry of thermal decomposition

 Graded Assignment SCI303B: Chemistry | Unit 5 | Lesson 8: Mid-Unit Test

Graded Assignment

Mid-Unit Test, Part 2

Answer the questions below. When you have finished, submit this assignment to your teacher by the due date for full credit.

(8 points)

Score
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This energy diagram is for the thermal decomposition of solid mercury (II) oxide (also known as mercuric oxide) into liquid mercury and oxygen gas.

A graph. The x-axis is labeled Reaction pathway. The y-axis is labeled Energy. A dashed horizontal line labeled Reactants is plotted at about one-fifth across the y-axis. A dashed horizontal line labeled Activated complex is plotted near the top of the y-axis. A line labeled Products is plotted on the graph. Products starts at the origin of Reactants, extends horizontally to the right, curves upward to the right with downward opening until Activated complex, slightly curves downward to the right, and extends horizontally to the right. The distance between Reactans and Activated complex is labeled (a).

Write a balanced equation for the reaction.

Explain what feature is shown by the arrow labeled (a).

Using chemical symbols and dashed lines (this can be done with type), draw what the activated complex or transition state might look like.

Is this reaction exothermic or endothermic? Explain.

Answer:

Question: The Equation For The Decomposition Of Mercury (II) Oxide 2HgO (s) –> 2Hg (s) + O2 (g) Change In H = 181.6 KJ If 167.0 KJ Of Heat Energy Is Absorbed By This Reaction, Will The Reaction Produce More Mercury (II) Oxide Or Consume The Mercury (II) Oxide?

Balanced equation: 2 HgO (s) – > 2 Hg (l) + O2 (g)

Reaction needs energy because energy of products is higher that energy of

Reactants, that’ how you find out is reaction exo- or endothermic

First off write out the reaction equation given,

HgO(g) -> O2(l) + Hg(g)

You will need to balance it.

The transition state for a reaction is the point where the reactant is structurally between products and reactant (this state exists for only an instant). Dashed lines in a chemical structure represent partial covalent bonds, essentially in a transition state they represent the bonds that are being broken and the new bonds being formed.

For example:

The reaction of CH3I + NaOH -> CH3OH + NaI

Attached is the transition state drawing, the brakets and double dagger symbol at the top is just standard notation for a transition state

The structure of O2 and HgO is simply O=O and Hg=O respectively.

1) 2HgO ——> 2Hg + O2

2) (a) Arrow show the difference between the energy of activated complex and energy of reactants.

3) ………Sorry here is confusion

4) It is endothermic reaction, because Graph show that the energy of product is greater than reactants, which mean reactants got energy by heating during the reaction, due to whic energy of products is high, so reaction is endothermic.

(8 points)

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The diagram below shows steps in the exothermic chemical reaction of bromomethane with hydroxide to form methanol and bromide ion. The black spheres are carbon atoms, the white spheres are hydrogen atoms, the red spheres are oxygen atoms, and the blue dots are bromine atoms.

Three molecular structures labeled A, B, and C. A. Two groups of circles. The first group is composed of a white and a red circle. To the right is a black circle in the middle with three small white and one large blue circles attached on it. B. Two groups of circles. The first group is composed of a red circle with a small white circle attached on it, attached to a black circle with three small white circles attached on it. To the right is a big blue circle. C. A group of circles. A small white circle is attached on a red circle. The red circle is attached to a black circle. Three small white circles are attached on the black circle. A big blue circle is attached on the black circle.

Write a balanced chemical equation to represent the reaction.

Using the figures in the diagram, draw the steps of the reaction in the correct order, label each molecule in the drawings, and describe what is happening in the reaction.

Draw an energy diagram of the reaction in which you label the energies of each step in the reaction and the activation energy.

Answer:

An energy diagram shows the amount of energy in a system over time. When you’re asked to draw an energy diagram, the format is usually the same depending on the kind of reaction (exothermic or endothermic). Here is the general format for this kind of question: https://imgur.com/7nx1f5a. The reactant(s) are usually the beginning (A). Then to start a reaction, activation energy must be added to reach the transition state (B). In an exothermic reaction, energy is released and exits the system, so for the products, the line goes down below the energy of the reactants (C).

I pretty much understood everything except this question…

2. The diagram below shows steps in the exothermic chemical reaction of bromomethane with hydroxide to form methanol and bromide ion. The black spheres are carbon atoms, the white spheres are hydrogen atoms, the red spheres are oxygen atoms, and the blue dots are bromine atoms.

• Write a balanced chemical equation to represent the reaction.

CH3Br + OH- → CH3OH + Br-

• Using the figures in the diagram, draw the steps of the reaction in the correct order, label each molecule in the drawings, and describe what is happening in the reaction.

• Draw an energy diagram of the reaction in which you label the energies of each step in the reaction and the activation energy.

(8 points)

Score
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This graph shows the rates of reaction in a chemical reaction with and without the addition of an enzyme.

Explain the shape of each line. What is happening to the reaction rate as the reactant concentration
is changed?

Explain what the enzyme appears to be doing.

Why does the curve of the reaction with enzyme flatten out?

Answer:

Enzymes will increase the rate of a chemical reaction by reducing the activation energy needed to make the reaction get started.

Explanation:

Enzymes are protein molecules which serve as catalysts for chemical reactions.

A catalyst is a substance which will decrease the activation energy for a reaction.

So why is this important? Enzymes will make reactions occur much more easily, quickly and more efficiently than they ever would without the enzyme.

Here is a video of an enzyme demonstration I like to share with my students. The video shows how an enzyme present in our saliva (spit) can aid in the process of digestion by acting on starches present in the foods we eat.

Make sure to pay attention to how quickly the starch changes with and without the added enzyme!

(8 points)

Score
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Draw an energy diagram for an endothermic reaction without a catalyst (use a solid line) and with a catalyst (use a dotted line). Label all parts of the diagram. Explain what a catalyst is and how a catalyst influences the rate of a reaction.

Answer:

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