143 EQULO397: pH, Ac and Bases Pre-Laboratory Assignment 1. Often solutions can
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143 EQULO397: pH, Ac and Bases Pre-Laboratory Assignment 1. Often solutions can be hazardous in ways that are not necessarily related to their acidity or basicity s Briefly comment on the hazards that you need to be aware of when working with (1) 1 × 10-2M HNOs solutions 12) 0.1M NH,/H,O solutions 2. A student performed an experiment similar to the one that you will perform, but using different solutions from the ones that you will use. The student's data are presented in Table 4 below. (1) Is a 0.1M solution of NaNO, acidic or basic? What experimental evidence supports your answer? (2) List the solutions studied by the student that are basic What experimental evidence supports your answer? Table 4 Student data for estimating the pH of solutions indicator color methyl violet methyl orange 0.1M solution red light blue yellow red violet violet violet violet violet red HNO C,H,NH, NaNO Ca(OH)b blue colorless blue yellow light pink red yellowExplanation / Answer
1.
a)
The solution of HNO3 is a strong oxidizing agent also. It can irritate skin, its vapor can irritate eyes (nitric acid is quite volatile).
b)
The ammonia solution contains a very volatile ammonia with systematic toxic effect on the living organisms and irritating action on the eyes.
2.
a)
The sodium nitrite solution is basic one due to the hydrolysis. A light pink color of phenolphthalein is the evidence.
b)
The solutions of NH2OH, C2H5NH2, NaNO2 and Ca(OH)2 were basic. The color of phenolphthalein is the evidence.
3.
Using the table data, we cannot make a conclusion about the relative basicity of the Ca(OH)2 and C2H5NH2 solutions: all the tests are of the same color.
4.
The order of increasing basicity is:
NaNO2 <NH2OH <C2H5NH2 <Ca(OH)2
The color of thymolphthalein allows distinguishing the basicity of the first three members of the above-mentioned series.
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