CHEM 1050 Study Guide - Comprehensive Final Guide: Rate Equation, Sodium Amalgam, Exothermic Welding

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28 Nov 2016

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In order to break a bond energy is needed. Forming a bond gives off energy ( that we can see as heat) State and changes of state: conditions that describe the state. If heat is given off exothermic-all combustions if heat is absorbed, endothermic of the system( mass, temp, volume) P, v, t are called state variables: given upper case symbols. State function: only depends on state of system; difference between start and end. Path: depends on how you got from start to finish. U : is the sum of the kinetic and potential energy of the particles making up the system. Heat is given symbol q and work is given symbol w. Q: is measured by determining temp change, which is converted from *c to joules: q= ccal x t, q= m x c x t if temp goes up qcal = +ve and therefore qchemical = -ve.

Related Questions

1.According to the following thermochemical equation, if 31.1 g of NO2 is produced, how much heat is released at constant pressure?how much heat is released at constant pressure?

2NO(g) + O2(g) â 2NO2(g);ÎHÂ° = â114.4 kJ

Select one:

a. 114.4 kJ114.4 kJ

b. 1.183Ã103kJ

c. 2.365Ã103kJ

d. 38.7 kJ

e. 1.088Ã105kJ

2.CalculateâââÎUâââof a gas for a process in which the gas absorbs ââ12 J ââof heat and does ââ20 Jââ of work by expanding.

Select one:

a. 8 J

b. 32 J

c. -32 J

d. 0, because âÎU is a state function

e. -8 J

3.If q = +56 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. is exothermic.

c. occurs rapidly.

d. is endothermic.

e. cannot occur.

4.If q = 18 kJ and w = 15 kJ for a certain process, that process

Select one:

a. requires a catalyst.

b. has an increase in internal energy.

c. occurs slowly.

d. is exothermic.

e. cannot occur.

5.What is the change in internal energy of the system (ÎU) if 10 kJ of heat energy is released by the system and â70 kJâ of work is done on the system for a certain process?

Select one:

a. â60 kJ

b. 80 kJ

c. 10 kJ

d. 60 kJ

e. â80 kJ

6.What is the quantity of heat evolved at constant pressure when ââ26.3 gââ H2O(l)ââ is formed from the combustion of H2(g) and O2(g)?

2H2(g) + O2(g) â 2H2O(l);ÎHÂ° = â571.6 kJ

Select one:

a. 15033 kJ

b. 15.03 kJ

c. 1.72Ã104âkJ

d. 417.6 kJ

e. 9.57Ã102âkJ

7.What quantity, in moles, of hydrogen is consumed when 76.8 kJ of energy is evolved from the combustion of a mixture of H2(g) and O2(g)?

H2(g) + O2(g) â2H2O(l);ÎHÂ° = â571.6 kJ

Select one:

a. 2.368 mol

b. 1.184 mol

c. 0.4223 mol

d. 0.2687 mol

e. 1.368 mol

8. Which of the following is an exothermic process?

Select one:

a. work is done by the system on the surroundings

b. heat energy flows from the system to the surroundings

c. work is done on the system by the surroundings

d. heat energy is absorbed by the system

e. none of the above

9. Which of the following statements is correct?

Select one:

a. Internal energy is not a state function.

b. The value of q is negative when heat flows into a system from the surroundings.

c. The value of q is negative in an endothermic process.

d. Heat flows from a system into the surroundings in an exothermic process.

e. Enthalpy is not a state function.

10.X2and F2react according to the following equation, forming XF. (X is an unknown diatomic element)

X2(g)+ F2(g)â2XF(g);ÎHÂ°=+271 kJ

If X2(g) and F2(g) were mixed in a thermally insulated vessel, the reaction that occurred would be

Select one:

a. endothermic, and the temperature of the reaction system would fall.

b. We could not tell unless the original and final temperatures were given.

c. exothermic, and the temperature of the reaction system would fall.

d. exothermic, and the temperature of the reaction system would rise.

e. endothermic, and the temperature of the reaction system would rise.

Question 2 Energy Calculations

a) Calculate the heat energy (q) when 12.0 g of water is heated from 20oC to 100oC. The

specific heat for water is given in your textbook.

b) Is the process of heating water exothermic or endothermic? Explain your answer.

Question 3 Energy Calculations

You dissolve 0.1 mol of ammonium nitrate in 100 mL of H2O. The temperature of the solution

changes from 22oC to 15oC. The specific heat capacity for water is 4.184 J/g.K. Show all

calculations on a separate sheet of paper!

a) Is this reaction endothermic or exothermic?

b) Calculate the heat, q, released or absorbed in the dissolution reaction.

c) Calculate the enthalpy change, ?Hrxn (kJ/mol), for dissolving 1 mol of ammonium nitrate.

Question 4. A gas expands from 264 mL to 971 mL at constant temperature. Calculate

the amount of work done in Joules by the gas when it expands against a constant pressure of 955

torr.

Question 5 Energy Calculations

a) The nutritional calorie (Calorie) is equivalent to 1 kcal. One pound (1.0 lb) of body fat is

equivalent to 4.1 x 103 kcal. Express this quantity in joules and kilojoules. Use

scientific notation for your answer!

b) If an athlete expends 1850 kJ/h (kilojoules per hour), how long does he have to exercise

to work off 1.0 lb of body fat?

c) The average amount of calories burned during running is 125 kcal/mile. How many

miles does this athlete have to run to burn off 1.0 lb of body fat?

Question 6

Calculate ?Ho for the following reactions at 298 K. Give the balanced thermochemical

equations and show the correct physical state in each equation. Calculate the enthalpy change

for each reaction. You will find thermochemical data in the back of your textbook in Appendix 3

(p. A-8 to A-12)

a) The formation of 1 mol of HCl (gas) from its elements

b) The formation of 1 mol of sodium chloride from its elements

c) The combustion of 1 mol glucose to water and carbon dioxide

d) HCl(g) + NH3(g) ? NH4Cl(g)

Question 7

Calculate heat of formation of SO2 under nonstandard state conditions, given the following

equations

SO2(g) +

1. What does a negative enthalpy value indicate about a chemical reaction?

1. Heat is required for the reaction and is located on the left of the reaction.

2. Heat is required for the reaction and is located on the right of the reaction.

3. Heat is released and is located on the left of the reaction.

4. Heat is released and is located on the right of the reaction.

2. 67 K is equivalent to:

is equivalent to:

4. Which of the following examples best represents heat?

1. A sample of platinum is

2. A piece of plastic contains 57 J of energy.

3. A piece of wood burns at

4. A toy car generates 45 J of kinetic energy.

5. Consider the combustion of propane

1. Is the combustion of propane endothermic or exothermic?

2. Is energy as heat released into the surroundings or absorbed by the system?

3. How much heat would this represent for the combustion of 3 moles of propane?

6. Calculate how much energy it takes to raise the temperature of 125 grams of aluminum from 100 to 245 degrees C. The specific heat of aluminum is 0.900 J/g degree C.

7. Calculate the heat change needed to raise the temperature of 1000 g of water from 5.0 degrees C to 95.0 degrees C.

8. How much energy is given off by the water in question number two if the 1000 g of water cools from 95.0 to 5.0 degrees C ?

9. Determine the specific heat of copper if it takes 10,500 J of energy to raise 520.0 grams of it from 27.0 degrees C to 245.0 degrees C

10. Determine the specific heat of an unknown element if it takes 540 J to raise the temperature of 55.6 grams of this element from 5.0 to 95.0 degrees C.

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CHEM 1050 Study Guide - Comprehensive Final Guide: Rate Equation, Sodium Amalgam, Exothermic Welding

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