# Solubility Rules & Reference Tables

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Solubility Rules & Reference Tables

Components of a Solution
Solute: substance being dissolved Ex: Salt, Sugar Solvent: substance doing the dissolving Ex: Water, Hexane

What Dissolves in What? Solute must form attractions to the solvent.
Polars dissolve polars Nonpolars dissolve nonpolars Polar solvents dissolve most ionic crystals

Solubility: How much solute can be dissolved in a
volume of solvent under certain conditions of temp. and pressure.

Using Reference Table G
Shows solubility in grams of solute per 100 grams of water at different temperatures

Saturated Solutions: hold max solute
possible at that temp. Table G: Solubility curves show saturation levels at different temps (in 100g of water).

Saturated Solutions are at EQUILIBRIUM.
Rate of dissolving = Rate of crystallization

Go to 50 °C and up to NaNO3 and over.
Ex: How many grams of NaNO3 are needed to create a sat. solution in 100g of water at 50 °C? Go to 50 °C and up to NaNO3 and over. Answer: 116 grams

Look at The Water!! Table G is for 100 grams of water.

How many grams of NaNO3 are needed to
create a sat. solution in 300g of water at 50 °C? Answer: 116 grams x 3 (three times as much water!) Or you can use a proportion: 116 grams = x grams 100 g H g H20

Unsaturated Solutions: could still hold
more solute at that temp. Would fall “below the line” on Table G Ex: 40 g of NaNO3 in 100g water at 50°

Supersaturated Solutions: hold more
solute than they should at that temp. Would fall “above the line” on Table G Ex: 140 g of NaNO3 in 100g water at 50°

How do Supersaturated Solutions Form?
Created a saturated solution at a high temp. and slowly let solution cool. Certain solutes can stay in solution (like sodium acetate).

solutions are unstable. Add just one more “seed crystal” to the
Supersaturated solutions are unstable. Add just one more “seed crystal” to the solution, all the excess solute will precipitate out quickly. Supersaturated Sodium Acetate solution after seed crystal added

Describe These Solutions
Saturated, Unsaturated or Supersaturated? 100 g NH4Cl at 70° in 100 g water 10 g SO2 at 10° in 100 g water 40 g NaCl at 90° in 100 g water

100 g NH4Cl at 70° in 100 g water Falls above the line (Supersaturated)

10g SO2 at 10° in 100g water Falls below the line (Unsaturated)

40g NaCl at 90° in 100g water Falls on the line (Saturated)

Concentrated Solutions:
have a lot of solute dissolved in the solvent Ex: Saturated solution of KI at 10° 135 grams in 100 g water = pretty concentrated

Dilute Solutions: only
have a little solute dissolved. Ex: Sat. solution of SO2 at 50° 4 grams in 100 g water = relatively dilute

Factors Affecting Solubility

Surface Area More contact between solute/solvent particles the faster it dissolves Crush substance into fine powder to dissolve faster. Use mortar and pestle

Stirring or Agitation:
Allows for more solute/solvent contact, and faster dissolving of solids and liquids However, stirring will disturb dissolved gases and cause them to come out of solution.

Temperature of Solvent
Higher temperature solvents will dissolve solid solutes faster Why? Solvent particles move faster making contact faster with solute.

Gases dissolve better when the temperature of the solvent is colder.
Ex: CO2 gas in hot soda (flat) vs. cold soda (fizzy)

Fish in aquariums need the dissolved oxygen in the water, if the temp gets too high they suffocate

Pressure Effects gas solubility only Why? Increasing pressure on a gas above a liquid causes more gas molecules to be “pushed” into solution.

The more particles already in solution the less solvent molecules available to dissolve new solute.

Miscible: liquids that dissolve in any proportions (ex: alcohol and water) Immiscible: liquids that do not dissolve in any proportion (ex: oil and water)

Electrolytes: Conduct electricity when dissolved in water

Why do they Conduct? Create mobile ions in solution.
The more concentrated the solution the more it conducts Includes: Soluble Ionic Compounds (ex: NaCl) Acids (ex: HCl) Bases (ex: NaOH)

Who Will Conduct? Which of the following compounds will conduct in solution? C6H12O6 LiBr KOH CH4 H2SO4 NO2

C6H12O6 Will Not (Covalent)
LiBr Will (Ionic) KOH Will (Base) CH4 Will Not (Covalent) H2SO4 Will (Acid) NO2 Will Not (Covalent)

Reference Table F Describes which ionic compounds are soluble or insoluble in water.

Why are Some Insoluble? Certain combinations of ions hold together so strongly that water cannot dissolve them into solution

Precipitates Precipitates are insoluble ionic compounds formed in double replacement reactions. Determine which product is the insoluble precipitate by using Table F.

You can separate a precipitate by filtration.
The solid will stay on the paper.

Is this soluble or not? CaCO3
Carbonate (CO3-2) is insoluble and Ca+2 as a partner is not an exception

Is this soluble or not? NaNO3
Nitrate (NO3-1) is always soluble, there are not exceptions

Is this soluble or not? Li3PO4
Phosphate (PO4-3) is insoluble, however, Li+1 is a Group 1 ion so it is an exception and the compound is soluble.

Soluble or Not? Look out for exceptions! CaSO4 MgSO4 PbCrO4 Li2S NH4OH

Insoluble CaSO4 Soluble MgSO4 Insoluble PbCrO4 Soluble Li2S Soluble NH4OH