Lab 3 Separation of a Mixture Prelab Questions Name Section Date 1. Look up some

Question

Lab 3 Separation of a Mixture Prelab Questions Name Section Date 1. Look up some of the properties of sand, salt, and ammonium chloride to complete this table. Melting Point Soluble in Water? Formula/Name Appearance NH,CI Ammonium Chloride Sio Silicon Dioxide (sand NaCI Sodium Chloride (salt) 2. What does 'to sublime" mean? 3. What does "to decant" mean? 4. What does "heat to constant mass" mean? 5. Why must a wet sample be heated to constant mass? 6. Why must an object never be weighed while it is hot? 7. If a sample of a salt-water solution weighs 8.24 g and after drying the salt weighs 2.15 g. What is the percent composition of the mixture? (26.1% salt and 73.9% water) Instructors Initials Lab 3 41

Explanation / Answer

1. Properties of sand, salt and ammonium chloride

Formula/Name : NH4Cl/ammonium chloride

Appearence : white solid

Melting point (M.P.) : 338 oC

Soluble in water : Yes

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Formula/Name : SiO2/Silicon dioxide

Appearence : Colorless solid

Melting point (M.P.) : 1710 oC

Soluble in water : No

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Formula/Name : NaCl/Sodium chloride

Appearence : white solid

Melting point (M.P.) : 801 oC

Soluble in water : Yes

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2. "to sublime" means to convert a solid directly into gaseous state without going to the liquid state.

3. "to decant" means to drain a liquid from a solid-liquid mixture without getting any solid in it.

4. "heat to constant mass" means heating a substance or a mixture till we get a constant weight of it. That is if a component is heat sensitive, it would get removed from the system and we would obtain a constant mass of the remainder at the end. Applicable in gravimetric analysis.

5. A wet sample has water which gets removed when heated to get a constant mass. This is necessary as the amount of water in the wet sample can vary and thus removal of water to get constant mass for further experiment and accurate result is a must.

6. An object is never weighed when hot as hot air in contact with the object causes fluctuation in the mass measured and the results are thus not accurate.

7. mixture of salt+water = 8.24 g

mass of salt = 2.15 g

mass% salt = 2.15 x 100/8.24 = 26.1%

mass% water = 73.9%

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