Section Pre-Laboratory Assignment 1. Read an authoritative source for a discussi

Question

Section Pre-Laboratory Assignment 1. Read an authoritative source for a discussion of the safe and proper way to insert a thermometer or glass tubing into a rubber stopper. Read an authoritative source for a discussion of graphing techniques. 2. A student doing this experiment was puzzled by the fact that while each of the individual solutions being used is dangerous, the mixture made by combining the two solutions is much less dangerous Actually, the resulting mixture could be safely disposed of by pouring it into the drain and diluting with a large amount of running water. Describe the hazards of each of the solutions. Explain why the mixture is not as hazardous as the original solutions from a waste-disposal point of view. student determined the AHneutan of nitric acid (HNO) mixed with NaOH solution, using the ocedure described in this experiment. Fifty milliliters of 1.00M HNOs was added to 50.5 mL o 0M NaOH solution, and the following time-temperature data were recorded. temp.,.C 24.7 24.8 24.9 time, min temp., 11.0 12.0 13.0 14.0 15.0 16.0 17.0 31.2 31 31 30 30 30 30.2 31.2 31.5

Explanation / Answer

1.

While inserting a thermometer or a glass tubing into a hole in a rubber stopper, lubricate the hole with water or glycerol. This facilitates the movement of the glass tubing or thermometer being inserted into the hole. Lubricate the ends of the glass tubing while inserting. Do not hold the glass directly with hands, instead use piece of cloth or work gloves. Hold the glass tubing close to where it enters the stopper.

Another method is to use a cork borer into the hole. It is used as a inserter. It slides into the hole and then tubing is inserted through it. It is then removed leaving the tubing into the hole. the tube can be eased into the hole by gentle twisting motion.

A titration curve is a graph of pH Vs the volume of titrant added. The titration curve is used to monitor the progress of the acid-base reaction. By graphing a curve, one can visualize the actual reaction that occurs during titration. When the titrant is a strong base, the pH gradually increases until the equivalence point. The pH jumps drastically at the equivalence point and then level off resulting in a 'S' shaped curve.

The curve can be graphed by noting volume of titrant to the horizontal axis and pH of the solution to the vertical axis, y axis. The graph then shows how pH changes during the titration.

2.

The given reaction involves Nitric acid, HNO3 and NaOH. Form the waste disposal point of view, it is not safe to dispose them directly as both are hazardous and corrosive chemicals.

HNO?3 is an acid and is corrosive. It can cause chemical burns on contact. Inhalation can cause ulcerations of nose, throat and larynx. It can cause ulcerations of skin, chemical burns on contact with eyes that can lead to permanent corneal damage. So it should be neutralized before disposing off.

NaOH is also very corrosive. It can attack the skin and can cause permanent damage to eyes. It should be neutralized before disposal.

The mixture of HNO3 and NaOH is safe to dispose as they get neutralized in the mixture. The neutralization reaction of HNO3 and NaOH produce salt and water. Hence, it is safe to dispose the mixture into the drain by diluting with lot of water.

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