HessPLspring2015

Topics: Thermodynamics, Chemistry, Sodium hydroxide Pages: 2 (358 words) Published: April 21, 2015
CH 110 Pre-Labrevised Spring 2015
HESS' LAW AND THE FIRST LAW OF THERMODYNAMICS

1.(a)IN YOUR OWN WORDS, explain how Hess’ Law (of constant heat summation) applies to the 3 chemical reactions that will be studied in this experiment

(b) Does the temperature decrease or increase for an exothermic reaction?

(c) Is energy released or absorbed for an exothermic reaction?

(d) What is the sign (positive or negative) for the ΔH of an exothermic reaction ?
(e) Use the heat capacity of the calorimeter given in the manual (top p. 34) and the equation at the top of p. 36 to calculate the heat gained by the calorimeter if the ΔT for a reaction was 7.06 °C.

2.Describe the procedure for this experiment. This can be in an outline format or a flow chart or paragraph format. It should not be copied directly from the manual. (This should be between ½ and one page, you may use the back of the page.)

3.Briefly discuss the safety precautions related to this experiment. (chemical and equipment related) CH 110

HESS' LAW AND THE FIRST LAW OF THERMODYNAMICS

Chemical Handling and Waste Treatment

Normal laboratory safety practices must be followed at all times. MSDS sheets are available in the laboratory.

Both the sodium hydroxide (NaOH) and the hydrochloric acid (HCl) solutions are corrosive solutions which are strong eye and skin irritants. If contact occurs, promptly flush exposed areas with lots of cold water and inform the instructor.

The solid sodium hydroxide pellets are very corrosive. Avoid contact with skin. If contact occurs, flush area as directed above. If the pellets are spilled, pick pellets up with a spatula, place in a beaker and dissolve with cold water. The resulting solution should be disposed of down the drain with lots of cold water Wipe area of spill (bench or floor) with lots of water and sponge.

The final...
Continue Reading

Please join StudyMode to read the full document

Become a StudyMode Member

Sign Up - It's Free