L07 Chem 151 Lecture 15: Spring Experiment 6 Lecture

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limehorse889

8 Mar 2017

School

WUSTL

Department

University College - Chemistry

Course

L07 Chem 151

Professor

Redden

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Document Summary

Part a use calorimetry and apply hess" law to determine hf of mgo. Part b use calorimetry to measure the amount of heat evolved for a neutralization reaction and determine the concentration of a strong base. Heat evolved from the system is absorbed by the solvent, raising its temperature. A reaction cannot be both endothermic and exothermic, but an exothermic process can combine with an endothermic one. Hess" law enthalpies of reaction can be added in the same manner as the reaction equations themselves because enthalpy is a state function. Heat of formation heat absorbed/evolved when 1 mole of the compound is produced from the reaction of the elements in their standard states. When there is no phase transition, q is proportional to t. C = heat capacity: the amount of heat required to raise the temperature of the object 1 degree celsius/kelvin (j/ c or j/k) Cp = the heat capacity at constant pressure.

Related Questions

1) What is the objective of this experiment? (Name of the experiment Introduction to Calorimetry)

A) To redefine Hess' Law.

B) To measure the light emitted from the reaction solution.

C) To measure the enthalpy of several acid-base reactions and to use these enthalpies along with Hess' law to determine the enthalpy of an acid base reaction not performed in the laboratory.

D)To study some of the properties of nable gases and thier reaction to acidic environments.

2) What is the SI unit for heat ?

A) Gallons.

B) Grams.

C) Moles.

D) Joules.

3) Which of the following has the units: J/gK?

A) Endothermic.
B) Specfic heat.
C) Enthalpy.
D) Heat capacity.

4) How would you define Specfic Heat (c)?

A) The amount of energy required to raise a mass one degree Celcius ( or Kelvin).

B) The change in temperature that occurs from one gram of substance releasing one Joule of energy.

C) The amount of heat required to raise one gram of a substance one degree Celcius (or Kelvin).

D) The amount of mass required to release one Joule of energy.

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