What should you do if a small amount of corrosive solution splashes on, hand or
ID: 493624 • Letter: W
Question
What should you do if a small amount of corrosive solution splashes on, hand or skin? b. Under what circumstances is it necessary that a reaction be carried out in the fume hood? c. What are the two items that you need to have on at all times while experiments are being performed in the laboratory ? A student weighed five 25.0 ml flasks and the following results were obtained: 29.97 g, 28.56 g, 29.55 g, 30.02 g. and 30.00 g. Calculate the average (mean) weight and the standard deviation from the mean. What is the mass of the 7 % NaCl solution if a student measured 50.50 ml of this solution and its density is 1.0486 g/ml. Express the answer to the correct number of significant figures. What do you refer to as: a. pure substance b. mixture Classify the following as a pure substance or a mixture: a. Ammonium Nitrate b. Carbon dioxide c. Soup d. PetroleumExplanation / Answer
1a) If a corrosive chemical splashes on the hand or skin, the affected area is to be immediately rinsed or washed with copious amounts of cold water. Thereafter, appropriate medication should be sought to prevent skin rashes or diseases.
b) In case a reaction emits gaseous products with or without obnoxious smell, it is imperative that the reaction be carried out in a fume hood. Often, when one is working with concentrated acids or alkalis, use of a fume hood is mandatory so that the harmful acid vapours can be easily sucked off by the hood. If one is working with gases or a reaction leads to generation of a gas, the use of a fume hood is absolutely essential.
c) Personal Protective Equipment like a lab coat and safety goggles are mandatory for working in the lab. When handling a chemical, the use of hand gloves is necessary.
2) Given, x = 29.97 g, 28.56 g, 29.55 g. 30.02 g, 30.00 g; we need to find the mean (x) and the standard deviation ()
x = x/n where n = number of measurements = (29.97 + 28.56 + 29.55 + 30.02 + 30.00)g/5 = 29.62 g (ans).
= (x - x)2/n = [(29.97 – 29.62)2 + (28.56 – 29.62)2 + (29.55 – 29.62)2 + (30.02 – 26.62)2 + (30.00 – 29.62)2]/5 = (1.5554/5) = 0.31108 = 0.5577 0.558 (ans).
3) We have a 7% NaCl solution meaning that 100 g of the solution contains 7 g NaCl.
Volume of solution taken = 50.50 mL; density of the solution is 1.0486 g/mL.
Therefore, mass of the solution = (volume of solution)*(density of solution) = (50.50 mL)*(1.0486 g/mL) = 52.9543 g.
Therefore, mass of NaCl contained in 52.9543 g solution = (52.9543 g solution)*(7 g NaCl/100 g solution) = 3.706801 g NaCl 3.7068 g NaCl (ans).
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