https://www.coursehero.com/file/59756712/613-Final-Exam-Semester-2-Examdocx/6.1.3 Final Exam: Semester 2 Exam Chemistry Sem 2
Points Possible: 100 Name:
Date: 3/4/2023
In this test, you will apply what you have learned in the semester. Answer the questions below. Submit this to your teacher when you are done.
Show all your work on this test.
Question 1: Energy in Matter (20 points)
A.A student put a bottle of water and a can of sugared soda in the freezer to
chill them quickly. When she took them out, the bottle of water was frozen but the can of soda was not. Explain why this happened. (8 points)
When you add something in water like sugar or salt, it lowers the fusion temperature and raises vaporisation temperature.
Adding salt or sugar changes the molality of the substance and makes it freeze at a lower temperature. This is why people put salt on streets of northern countries to prevent people slipping on ice (it makes water liquid at temperatures
lower than normal melting point).
This is also why you add salt to boiling water (which makes it boil at a temperature higher than 100 C) to cook food faster.
B.A passenger on an airplane finished a 0.5 L bottle of water during the flight and replaced the lid. The cabin pressure and temperature were maintained at 0.75 atm and 295 K during the flight. After landing, he noticed his empty water bottle had collapsed. (12 points)
i.How many moles of gas were in the water bottle? (6 points)
n = 75 x 0.5 /8.3 x 295 = 0.0153 moles of gas 2
https://www.coursehero.com/file/59756712/613-Final-Exam-Semester-2-Examdocx/ii.If the pressure after landing was 1.0 atm, what was the volume of the passenger's collapsed water bottle? (Assume the bottle collapsed easily and temperature didn't change.) (6 points)
375 mL
Question 2: Equilibrium and Kinetics (20 points)
A.Formic acid is a weak acid found in insect stings. It partially dissociates in water according to the reaction HCHO2CHO2– + H+. The equilibrium constant describing the
dissociation is Ka =. (6 points)
i.If a solution of formic acid contains 0.2 M HCHO2, 0.006 M CHO –, and 0.006 M H+, what is the Ka of the acid? (4 points)
1.8x10^-4 M
ii.What is the pH of the solution at the concentrations given? (4 points)
pH=2.22
iii.What would happen to the equilibrium position if more CHO2– were added to the solution? (4 points)
There is 1 mol on the left side and 2 mols on the right side of the equilibrium.If more HCO2- were added to the right side the equilibrium, it would shift to the left to produce more HCHO2.
Points Possible: 100 Name:
Date: 3/4/2023
In this test, you will apply what you have learned in the semester. Answer the questions below. Submit this to your teacher when you are done.
Show all your work on this test.
Question 1: Energy in Matter (20 points)
A.A student put a bottle of water and a can of sugared soda in the freezer to
chill them quickly. When she took them out, the bottle of water was frozen but the can of soda was not. Explain why this happened. (8 points)
When you add something in water like sugar or salt, it lowers the fusion temperature and raises vaporisation temperature.
Adding salt or sugar changes the molality of the substance and makes it freeze at a lower temperature. This is why people put salt on streets of northern countries to prevent people slipping on ice (it makes water liquid at temperatures
lower than normal melting point).
This is also why you add salt to boiling water (which makes it boil at a temperature higher than 100 C) to cook food faster.
B.A passenger on an airplane finished a 0.5 L bottle of water during the flight and replaced the lid. The cabin pressure and temperature were maintained at 0.75 atm and 295 K during the flight. After landing, he noticed his empty water bottle had collapsed. (12 points)
i.How many moles of gas were in the water bottle? (6 points)
n = 75 x 0.5 /8.3 x 295 = 0.0153 moles of gas 2
https://www.coursehero.com/file/59756712/613-Final-Exam-Semester-2-Examdocx/ii.If the pressure after landing was 1.0 atm, what was the volume of the passenger's collapsed water bottle? (Assume the bottle collapsed easily and temperature didn't change.) (6 points)
375 mL
Question 2: Equilibrium and Kinetics (20 points)
A.Formic acid is a weak acid found in insect stings. It partially dissociates in water according to the reaction HCHO2CHO2– + H+. The equilibrium constant describing the
dissociation is Ka =. (6 points)
i.If a solution of formic acid contains 0.2 M HCHO2, 0.006 M CHO –, and 0.006 M H+, what is the Ka of the acid? (4 points)
1.8x10^-4 M
ii.What is the pH of the solution at the concentrations given? (4 points)
pH=2.22
iii.What would happen to the equilibrium position if more CHO2– were added to the solution? (4 points)
There is 1 mol on the left side and 2 mols on the right side of the equilibrium.If more HCO2- were added to the right side the equilibrium, it would shift to the left to produce more HCHO2.
