Chem: Lab Report: Identifying An Unknown Compound 5m3b6

LAB REPORT IDENTIFYING AN UNKNOWN COMPOUND

PURPOSE To determine the properties of six compounds and design an experiment to identify an unknown substance.

PROCEDURES Baking soda (sodium bicarbonate, ), washing soda (sodium carbonate, ), chalk (magnesium carbonate, ), table salt (sodium chloride, ), cornstarch and Epsom salt (magnesium sulphate heptahydrate, · 7 ) were tested for five different characteristics: solubility in water, reaction with acetic acid, reaction with tincture of iodine, reaction with sodium hydroxide (with water mixture) and reaction with phenolphthalein (with water mixture). The results of these tests were placed in a table (Table 1) for use later. The next part of this experiment is to test six unknown compounds using the information found in the previous step. This, however, can only be done if there is a constant procedure that can be used for each of the unknowns, that will in the end yield the identity of the compound. My procedure took the form of a flow-chart:

Jonathan Sterling

Jonathan Sterling

All Chemicals (add water)

pale pink: sodium bicarbonate

soluble

insoluble

(add phenolphthalein)

(add tincture of iodine)

bright pink: sodium carbonate

no reaction

black colour: cornstarch

(add acetic acid)

(add sodium hydroxide)

no reaction: sodium chloride

no reaction: yellow colour

cloudy: magnesium sulfate heptahydrate

fizzes: manesium sulphate

DATA

PROPERTIES OF SIX KN KNOWN COMPOUNDS

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Reaction with Iodine Tincture

Reaction with Sodium Hydroxide

Reaction with Phenolphthalein

no reaction

reaction: pale pink colour

reaction: fizzed

no reaction, yellow/orange colour no reaction, yellow colour

no reaction

reaction: fizzed

no reaction, yellow colour

no reaction

reaction: hot, bright pink colour reaction: medium pink colour

Soluble in Water

Reaction with Acetic Acid

Sodium bicarbonate

yes

reaction: fizzed

Sodium carbonate

yes

Magnesium carbonate

no

Compound

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Sodium chloride

yes

no reaction

Cornstarch

no

no reaction

Magnesium sulphate heptahydrate

yes

no reaction

no reaction, very dark colour reaction: black precipitate formed no reaction, yellow colour

no reaction

no reaction

no reaction

no reaction

reaction: white, cloudy precipitate

no reaction

TABLE 1. THE PROPERTIES OF SIX COMPOUNDS

PROPERTIES OF THE SIX “UNKNOWNS”, AND THEIR IDENTITIES Sample Designation

Step 1.

Step 2.

Sample A.

soluble in water.

phenolphthalein: bright pink

Sample B.

soluble in water

phenolphthalein: no reaction

sodium hydroxide: cloudy

Sample C.

soluble in water

phenolphthalein: no reaction

sodium hydroxide: no reaction

Sample D.

insoluble in water insoluble in water

iodine tincture: black iodine tincture: yellow

soluble in water

phenolphthalein: pale pink

Sample E.

Sample F.

Step 3.

acetic acid: fizzed

TABLE 2. THE IDENTITIES OF THE SIX “UNKNOWN” COMPOUNDS

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Compound sodium carbonate (washing soda) magnesium sulphate heptahydrate (Epsom salt) sodium hydroxide (table salt) cornstarch magnesium sulphate (chalk) sodium bicarbonate (baking soda)

Jonathan Sterling

CONCLUSIONS

SOURCES OF ERROR There was no error; all the results were exactly as expected.

QUESTIONS FOR FURTHER THOUGHT 1. Compare qualitative and quantitative analysis. Qualitative uses refers to results in description and narrative form, whereas quantitative uses refers to results with numbers, and quantities. 2. Did this experiment use qualitative or quantitative analysis? Explain. This experiment used qualitative analysis; there were no numbers, values, or calculations in this experiment. All that was needed were observations on the reactions.

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