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Indicators and pH

Indicators and pH. Objective:. To learn about pH and how indicators show a substance to be an acid or a base. Research:. Acid: solutions – high concentration of H 3 O + ions. Hydronium Base: solutions – high concentration of OH - ions. Hydroxyl

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Indicators and pH

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  1. Indicators and pH Objective: To learn about pH and how indicators show a substance to be an acid or a base.

  2. Research: • Acid: solutions – high concentration of H3O+ ions. Hydronium • Base: solutions – high concentration of OH- ions. Hydroxyl • pH: percent of hydrogen – how acidic it is.

  3. pH scale: series of numbers 0-14. 7= neutral, 0-6 acid, 8-14 base. • Indicator: substance that shows a definite color change when mixed with acid or base.

  4. Effect on AcidsEffect on Bases • Blue litmus paper: pink___ • Red litmus paper: ___ blue • Phenolphthalein: stays clearshocking pink • Bromthymol blue: orange ___ • Congo red: blue ___ • As the pH of a solution changes, the indicator shows a specific color change.

  5. Procedure I – AcidAfter each step, record your observations. • Drop a small drop of HCl onto blue litmus paper. • Drop a small drop of HCl onto red litmus paper. • Place a small amount of HCl into test tube A.Add 1 drop of phenolphthalein. Rinse TT. • Place a small amount of HCl into test tube A.Add 2 drops of bromthymol blue. Rinse TT. • Place a small amount of HCl into test tube A.Add 1 drop of congo red. Rinse TT.

  6. Procedure II – BaseAfter each step, record your observations. • Drop a small drop of NaOH onto blue litmus paper. • Drop a small drop of NaOH onto red litmus paper. • Place a small amount of NaOH into test tube B.Add 1 drop of phenolphthalein. Rinse TT. • Place a small amount of NaOH into test tube B.Add 1 drop of bromthymol blue. Rinse TT. • Place a small amount of NaOH into test tube B.Add 1 drop of congo red. Rinse TT.

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