Alex T. ZhaoGreg KerrIB Chem HLSeptember 7, 12

Separation of mixtures by Filtration and crystallization

Background: The separation of a mixture of two solids can often be achieved by filtration and crystallization. To be successful this requires that the components of the mixture have different solubilities in a particular solvent.

Aim: Purpose of this experiment is to separate a Sodium Chloride charcoal mixture by filtration, and a Copper (II)/Chloride mixture by crystallization.

Equipment required: Balance Filter funnel stand Filter funnel Hotplate Watch glass Glass rod Beakers (two 100mL) Graduated cylinder (25 mL

Filter paper Sodium chloride/charcoal

mixture (4g) Sodium chloride/copper(II)

chloride mixture (8g) Ethanol (25mL) Distilled water Boiling chip

Part A: Separation of a Sodium Chloride and Charcoal Mixture.Observations:

Sodium Chloride/charcoal mixture: powder, solid, opaque, smooth in texture, odorless, slivery grey, traces of white, crystalline particles (salt)

NaCl Crystals after separation: White, crystalline, solid, opaque, odorless, grainy (not fine), powdery (to some extent)

Charcoal: Smooth, solid, silvery grey, opaque, odorless, powdery, fine.

Part B: Partial Separation of a Sodium Chloride and Copper (II) Chloride Mixture.

Observations: Copper (II) Chloride/Sodium Chloride

solution: Graining, solid, opaque, odorless. Copper (II) Chloride is of bluish green, Sodium Chloride is grainy, whitish crystals.

The solid filtered out is dark green, with small traces of blue, odorless crystals, solid, opaque.

Filtrate: Clear, transparent, liquid, bluish green After the solid filtered is washed with ethanol, it turns lighter

in color, and turns from a dark bluish green to greenish white/milky green color. Other physical properties retain. This

IB Chemistry HL Lab 2 September 7, 2012

implies that the solid is actually Sodium Chloride, and not Copper (II) Chloride.

Part C: Separation of a Sodium Chloride and Copper (II) Chloride Mixture.Observations:

Appearance of Solid: Crystalline, solid, opaque, dark greenish, solid, opaque, odorless, grainy

Appearance of filtrate: Clear, transparent, dark bluish green, odorless.

Processing results, and questions:1. In part A, the solubility of sodium chloride in water allowed us to separate

it from charcoal. When the mixture of solids was stirred into the water, the NaCl (salt) dissolved completely while the charcoal remained undissolved. When the mixture is filtered, the charcoal is filtered out, while the filtrate is really salt water. Heating the filtrate then boils of the water, leaving us with salt crystals

2. In part B, we separated out some pure sodium chloride, but the filtrate contained both sodium chloride and Copper (II) Chloride. By heating the water in the first place, we are increasing the solubility of substances in water slowly. The fact that some of the sodium chloride was filtered out shows that as the water heated up, most of the copper (II) chloride became dissolved (thus came out in filtrate), while only some of the Sodium Chloride was dissolved (some came out in filtrate and some were filtered out.) This implies that the solubility of Copper (II) Chloride’s in water is better than that of Sodium Chloride.

3. Lastly in part C, using ethanol as a solvent, we were able to completely separate sodium chloride and copper (II) chloride. This is because salt barely dissolves in ethanol, while copper (II) chloride dissolves very well in the ethanol. Hence, the salt is easily filtered out, while the copper (II) chloride passes through the filter paper as filtrate while dissolved in ethanol. These facts show that copper (II) chloride is significantly more soluble in ethanol than in water (in which case we couldn’t completely separate sodium chloride and copper (II) chloride).

IB Chemistry HL Lab 2 September 7, 2012