Exam (elaborations)
Chem Test 3
- Course
- Institution
Exam of 4 pages for the course Chem1050 at U of G (Chem test)
[Show more]
Seller
Follow
barb123
Content preview
NUCLEUS HIGH SCHOOLUnit Test Unit - Rates of Reaction
KNOWLEDGE/UNDERSTANDING
1. Which statement does not describe an endothermic reaction? (1)
a. The surroundings cool down.
b. ΔH°rxn is positive.
c. Heat is released by the system.
d. Heat is absorbed by the system.
e. The potential energy of the products is greater than the potential energy of the
reactants
2. A chemical reaction is carried out in a coffee cup calorimeter. The temperature of
the water changes from 25.2 °C to 19.8 °C. Which statement is correct? (1)
a. The water loses energy, so the reaction is exothermic.
b. The water gains energy, so the reaction is exothermic.
c. The water loses energy, so the reaction is endothermic.
d. The water gains energy, so the reaction is endothermic.
3. The reaction 2 CO(g) + O2 (g) → 2 CO2 (g) is exothermic. (3)
a. What is the sign of Δ H for this reaction?
i. The sign of ΔH for the exothermic reaction 2 CO(g) + O2(g) → 2 CO2(g) would
be negative
b. Draw an enthalpy diagram for this reaction.
i.
c. What is the sign of Δ H for the reverse reaction?
i. For the reverse reaction, which would be the conversion of 2 CO2(g) into 2 CO(g)
+ O2(g), the sign of ΔH would be the opposite of the forward reaction. Since the
forward reaction is exothermic (ΔH < 0), the reverse reaction would be
endothermic (ΔH > 0) (positive). In an endothermic reaction, heat is absorbed
from the surroundings, resulting in an increase in the enthalpy of the system.
4. Describe two ways in which temperature affects the rate of reaction? (2)
a. Firstly, when the temperature rises, all of the molecules involved in the reaction start to
gain more energy and move faster. This increased energy and speed lead to frequent
collisions between the reacting molecules. The more collisions occur, the higher the
chances of successful collisions, where the molecules collide with enough energy to
break bonds and form new ones. As a result, the reaction rate increases with temperature
due to the increased collision frequency.
b. Secondly, higher temperatures also make collisions more energetic. When molecules
collide with sufficient energy, they can overcome the activation energy barrier required
for the reaction to occur. Activation energy is the minimum energy needed for a chemical
reaction to start. By increasing the temperature, more molecules possess the necessary
energy to surpass this barrier, leading to a greater proportion of successful collisions.
5. What is the difference between specific heat capacity and heat capacity? (2)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller barb123. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $8.19. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
67474 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now