Indicator Lab Init: 5/25/2011 by Daniel R. Barnes
Our Samples: • H2O • 2. H2SO4 • NaCl • NaOH • HCl • NaHCO3 • NaClO • NH3 • CH3COOH • 10. CH3CHOHCH3 • 11. C12H22O11 • 12. CuSO4
Your liquid indicator in this lab is . . . phenolphthalein
This is a drop plate. It has twelve wells in it. well well well well well well well well well well well well
The color code chart in the pH paper container applies only to the pH paper. It does NOT apply to the litmus paper. pH paper Color code chart pH paper blue litmus paper red litmus paper
Please do the lab before proceeding any further. Thank you.
water 1. H2O base acid Hydrogen hydroxide Hydronium hydroxide
+ + H H H H H H O O O O O O S sulfuric acid 2. H2SO4 H2SO4 + H2O H3O+ + HSO4- strong acid HSO4- + H2O D H3O+ + SO42- weak acid “weak” dissociation + “STRONG” dissociation +
sodium chloride 3. NaCl “table salt” NaCl(cr) Na+(aq) + Cl-(aq)
“lye” sodium hydroxide 4. NaOH NaOH(cr) Na+(aq) + OH-(aq) base
hydrogen chloride 5. HCl hydrochloric acid acid HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)
6. NaHCO3 sodium hydrogen carbonate sodium bicarbonate baking soda NaHCO3(cr) D Na+(aq) + HCO3-(aq) HCO3-(aq) + H3O+(aq) D H2CO3(aq) + H2O(l) base
7. NaClO sodium hypochlorite bleach ? H2O NaClO(cr) Na+(aq) + ClO-(aq) ClO-(aq) + H3O+(aq) HClO(aq) + H2O(l) base http://www.bioworldusa.com/household/ph-scale-comparisons says the pH of bleach is 12.6
Ion Corner The hypochlorite ion found in liquid chlorine bleach is just one of a series of chlorine-containing species. Cl2 = “chlorine” Cl- = “chloride” ClO- = “hypochlorite” ClO2- = “chlorite” ClO3- = “chlorate” ClO4- = “perchlorate”
8. NH3 ammonia ammonium hydroxide NH3(g) + H2O(l) NH4+(aq) + OH-(aq) base
9. CH3COOH acetic acid ethanoic acid vinegar CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO-(aq) acid
10. CH3CHOHCH3 isopropanol base ? isopropyl alcohol rubbing alcohol The OH in an alcohol molecule doesn’t come off in water. H H C C C H H H H H
11. C12H22O11 sucrose base ? table sugar The OH in a sugar doesn’t come off in water.
12. CuSO4 copper sulfate CuSO4 Cu2+(aq) + SO42-(aq) Cu2+(aq) + 2OH-(aq) Cu(OH)2(cr) acid SO42-(aq) + H3O+(aq) HSO4-(aq) + H2O(l) base A 0.2M solution is said to have a pH of 4.
CONCLUSIONS: 1. What is the relationship between the pH of a sample and its effect upon the two colors of litmus paper? Your results may not be exactly the same as everyone else’s, so you have to answer the question based on your data. However, here’s what wikipedia says: “Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic (i.e. alkaline) conditions, with the color change occurring over the pH range 4.5-8.3 at 25 °C. Neutral litmus paper is purple.” That’s not quite as simple as what I was brought up to believe, but what we are taught in school is often an over-simplification of reality.
Blue (top) and red (bottom) litmus paper. When litmus paper is placed in acid, the red stays red (bottom right) and the blue turns red (top right). When litmus paper is placed in base, the blue stays blue (top left) and the red turns blue (bottom left).
CONCLUSIONS: 2. What liquid indicator did you use? What is the relationship between the pH of a sample and the color it turned when the liquid indicator was mixed with it? We used phenolphthalein as our liquid indicator in this lab. Click me to remove me If the pH was less than or equal to 7, the phenolphthalein remained clear. Click me to remove me If the pH was greater than 7, the phenolphthalein turned hot pink (fuchsia/magenta). Click me to remove me Click me to remove me