Question

Name: Tear this page out of your laboratory manual and submit it to your TA with your answers, B. Post-Lab Assessment Questions: (15 pts) 1. (1 pts) Sodium Hydroxide is a chemical that is found in drain cleaners and as a component of soaps. Is Sodium hydroxide an acid or a base? 2. (10 pts) Using the information below and the table provided, estimate the pH of a 1 M solution of sodium bisulfate (NaHSO4). • When phenolpthalein is added to 1 M NaHSO, the resulting solution is colorless. • When thymol blue is added to 1 M NaHSO, the resulting solution is yellow. • When methyl violet is added to 1 M NaHSO, the resulting solution is violet. Indicator Solution Methyl Violet Thymol Blue Methyl Orange Bromothymol Blue Phenolphthalein pH range in which the color changes 0.5 - 2.0 1.2 - 2.8 8.2 - 9.1 3.1 -4.4 6.0 -7.6 8.0 -9.8 Color Change of indicator Yellow to Violet Red to Yellow Yellow to Blue Red to Yellow Yellow to Blue Colorless to Red 3. (2 pts) Which of the indicators in the table above would be the best to use if you wanted to observe changes in a solution at around pH 7? 4. (2 pts) If you added Thymol blue to a solution of pH 5 what color would you observe? fyrriment 7

Answer 1

1. Sodium Hydroxide, Chemical foreniala NOOH, e's a base (strong base) .. ( rom 2 from the imat inloomation belowd estimating the pH of ICM) Natsoa soin. • Wher phenolp thalein is add to 11M) NaHSO4 SOLM, the resulting solo ó colounless — phenolpthalein changes colourse colourless to red'in a pH rašge 8.0-9.8 (provide in the resulting soon boss not esged is colourless after adding phenolp thalin. the table) Cote Conclusion: pH of I(M) NaHSO4 Solor is less than on gwa touche de granber than Sinoni equal to 8.00, greater than 8.00 at all • When thymol blue is added to I (M) Nahts04 SOLO the resulting color is yellow. . thymol blue changes colours from Red to yellon in a pH sange 1.2-2.8 and it again changes colour from yellow to Blue in ph nange 8.2-9.1. the resulting soll is yellow when theyoud blue baw. U - Conclusion - PNOY ICM) NaHSO4 is greater than on equal to 2.8 but less than on equal to 8.2.

• When methyl violet is added to ICM) Nansoa som the nesulting soil is violet. Methyl violet changes colour from 'Yellow to violet in ph sange 0.5-2.0. the resulting som has tonna violet whor methyl violet Vis addw. Conclusion - pH of 1(M) No NSA soil is greaten. than on equal to 2.00 Final conclusioor => Cossidening previous three conclusions we have neache to a final conclusion that by the provide data, we can only predict a range of pH of 16M) Nansoa soin And the sange of pH is 2.00-8.00 But as we know Nawson is an acid salt, probably the pH value won't excen & PF =10 . " 3. pH= 7 is neutral pH. So, the soln is neithers acidic non basic . Bromothymol blue would be a suitable indicaton if you want to observe changes around PNZ . Adding Thyono blue to a son of pH 5 would show yellow colours becaus the provided chart we can see from PH 2.8 to 8.2 the colour would be yello nom
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