Bromothymol blue substitute

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Lab Report Assistant

This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Exercise 1: Using pH Paper and the Indicator Bromothymol Blue (BTB)

Data Table 1. Data Collected from Exercise 1.

ID Number

Chemical Name

Chemical Formula

Hypothesis: Acid or Base

pH

BTB Color

Acid or Base?

11A

Acetic acid

CH3COOH

Acid

pH 2

Yellow

Acid

11B

Nitric acid

HNO3

Acid

pH 3

Yellow

Acid

11C

Sulfuric acid

H2SO4

Acid

pH 3

Yellow

Acid

11D

Phosphoric acid

H3PO4

Acid

pH 2

Yellow

Acid

11E

Sodium acetate

CH3COONa

Base

pH 7

Blue

Base

11F

Sodium bicarbonate

NaHCO3

Acid

pH 8

Blue

Base

11G

Sodium dihydrogen phosphate

NaH2PO4

Base

pH 0

Yellow

Acid

11H

Sodium hydrogen sulfate

NaHSO4

Acid

pH 6

Yellow

Acid

12A

Sodium hydrogen sulfite

NaHSO3

Acid

pH 5

Yellow

Acid

12B

Limewater

Ca(OH)2

Base

pH 9

Blue

Base

12C

Sodium phosphate

Na3PO4

Base

pH 13

Blue

Base

12D

Sodium hydrogen phosphate

Na2HPO4

Base

pH 7

Blue

Base

12E

Ammonium hydroxide

NH4OH

Base

pH 8

Blue

Base

12F

Hydrochloric acid

HCl

Acid

pH 2

Yellow

Acid

12G

Sodium carbonate

Na2CO3

Base

pH 10

Blue

Base

12H

Sodium hydroxide

NaOH

Base

pH 12

Blue

Base

Questions

A. When you created hypotheses to guess whether each chemical was an acid or base, what specifically did you look for in the chemical formulas?

I looked for OH- or H+ in the formula and if it was an H+ than the chemical is most likely acidic and OH- would be basic.

B. What is the value of using pH paper as an indicator?

You could find if it were a weak or strong acid or base by looking at the pH paper. With the pH paper, you would be able to determine the substances pH value number and not just if it’s acidic or basic.

C. What is the value of using BTB as an indicator? When might BTB be a better choice than pH paper?

To figure out the pH value we must add the BTB, green means it's natural, blue is base, and yellow is acidic. It’s useful to do this whenever you want to know if any chemical is acidic or basic.

D. Write the chemical equation of mixing nitric acid (HNO3) with water.

HNO3 (aq)+ H2O(aq) <—>H3O++NO3-

E. Write the chemical equation of mixing ammonia (NH3) with water.

NH3(aq) H2O —>NH4+(aq)+ OH-(aq)

F. What are the conjugate acids and conjugate bases of questions D and E?

The conjugate bases of D and E are NO3-and OH