# Solutions Chapter 14.

## Presentation on theme: "Solutions Chapter 14."— Presentation transcript:

Solutions Chapter 14

solution Homogeneous mixture of 2 or more substances in a single physical state particles in a solution are very small particles in a solution are evenly distributed particles in a solution will not separate

solute The substance that is dissolved examples: sugar, salt

solvent Aqueous solutions-use water as solvent
Substance that does the dissolving example: water, ethanol Aqueous solutions-use water as solvent

Like dissolves like A solute will dissolve best in a solvent with similar intermolecular forces. If the intermolecular forces are too different the solute will not dissolve in that solvent.

Calculating the strength of a solution
Often the strength of a solution can be expressed in terms of percent.

Percent Solutions can be calculated 2 ways.
% by volume This compares the volume of solute to the total volume of solution. % by mass This compares the mass of solute to the total mass of solution. Percent Solutions The percent composition of a solution can be expressed two possible ways. % by volume or mass Let’s first discuss percent by volume. Percent by volume ( % (v/v)) = Volume of solute / Volume of solution x 100%

Volume Percent Volume of solute present in a total volume of solution.
Volume Percent (v/v) = volume of solute / volume of solution x 100%

Calculating volume percent
A solution is prepared by dissolving 36 ml of ethanol in water to a final volume of 150 ml what is the solution’s volume percent? % (v/v) ethanol = 36 ml ethanol / 150 ml total x 100% Volume Percent ethanol = 24 %

Volume percent If 15.0ml of acetone is diluted to 500ml with water what is the % (v/v) of the prepared solution? % (v/v) = 15.0ml / 500ml x 100% % v/v = 3.0% acetone

Mass percent Way to describe solutions composition
mass of solute present in given mass of solution mass percent = mass of solute mass of solution grams of solute grams of solute + grams of solvent X 100 X 100

Mass percent A solution is prepared by dissolving 1.0g of sodium chloride in 48 g of water. The solution has a mass of 49 g, and there is 1.0g of solute (NaCl) present. Find the mass percent of solute.

Mass Percent A solution is prepared by mixing 1.00g of ethanol, C2H5OH, with g of water. Calculate the mass percent of ethanol in this solution.

Solubility The extent to which a solute will dissolve
expressed in grams of solute per 100g of solvent ‘likes dissolve likes’

Not every substance dissolves in every other substance
soluble- capable of being dissolved salt insoluble- does not dissolve in another oil does not dissolve in water

Solubility & liquids Miscible- two liquids that dissolve in each other completely immiscible- liquids that are insoluble in one another oil & vinegar

The compositions of the solvent and solute will determine if the substance will dissolve
stirring temperature surface area of the dissolving particles

A solution is prepared by mixing 2
A solution is prepared by mixing 2.8 g of sodium chloride with 100 g of water. What is the mass percent of NaCl? What is the volume percent alcohol when you add sufficient water to 700mL of isopropyl alcohol to obtain 1000mL of solution?

saturated solution contains the maximum amount of solute for a given quantity of solvent no more solute will dissolve

unsaturated solution contains less solute than a saturated solution
could use more

Supersaturated solution
Solution contains more solute than it can ‘hold’ too much

Dilute solution- contains a small amount of solute
Concentrated solution- contains large amount of solute

Solubility Table salt: at room temperature, 37.7 g can be dissolved in 100 ml of H2O Sugar: at room temperature, 200 g can be dissolved in 100 ml of H2O

Solubility Curve

Solubility curve Determines solubility of substances at specific temperatures with raising temperature solids increase in solubility with increase in temperature gases decrease in solubility ex: fish die

on the line- saturated (can not hold anymore) above the line- supersaturated (holding more than it can) below the line- unsaturated (can hold more solute) supersaturated Solute (g) per g H2O saturated unsaturated temperature

92 g of NaNO3 are added to 100ml of water at 25°C and mixed
92 g of NaNO3 are added to 100ml of water at 25°C and mixed. What type of solution is it? 80 g of NaNO3 are added to 100ml of water at 25°C and mixed. What type of solution is it?

What is the solubility of NaNO3 in 100g of H2O at 20°C?

Concentration of solutions
Concentration of a solution is the amount of solute in a given amount of solvent most common measurements of concentration are: molarity (mole fraction)

Concentration of solutions
Concentration of a solution is the amount of solute in a given amount of solvent most common measurements of concentration are: molarity (mole fraction)

Molarity Number of moles of solute per volume of solution in liters
molarity (M) = liters of solution mol L

Molarity Calculate the molarity of a solution prepared by dissolving 11.5g of solid NaOH in enough water to make 1.50 L of solution. Given: mass of solute = 11.5 g NaOH vol of solution = 1.50 L molarity is moles of solute per liters of solution

Molarity Convert mass of solute to moles (using molar mass of NaOH). Then we can divide by volume molar mass of solute = 40.0 g 11.5 g NaOH x 1 mol NaOH 40.0 g NaOH 0.288 mol NaOH 1.50 L solution = mol NaOH = M NaOH

Molarity Calculate the molarity of a solution prepared by dissolving 1.56 g of gaseous HCl into enough water to make 26.8 mL of solution. Given: mass of solute (HCl) = 1.56 g volume of solution = 26.8 mL

Molarity Molarity is moles per liters
we have to change 1.56 g HCl to moles HCl and then change 26.8 mL to liters molar mass of HCl = 36.5 g 1.56 g HCl x 1 mol HCl 36.5 g HCl = mol HCl = 4.27 x 10-2 mol HCl

Molarity Change the volume from mL to liters 1 L = 1000 mL 26.8 mL x 1 L 1000 mL = L = 2.68 x 10-2 L

molarity Finally, divide the moles of solute by the liters of solution molarity = x 10-2 mol HCl 2.68 x 10-2 L = 1.59 M HCl

molarity Calculate the molarity of a solution prepared by dissolving 1.00 g of ethanol, C2H5OH, in enough water to give a final volume of 101 mL.

molarity One saline solution contains 0.90 g NaCl in exactly 1.0 L of solution. What is the molarity of the solution?

molarity A solution has a volume of 250 mL and contains 0.70 mol NaCl. What is its molarity?

dilution Diluting a solution:
reduces the number of moles of solute per unit volume the total number of moles of solute in solution does not change

Diluting solutions M1V1 = M2V2
M1 = molarity of stock solution (initial) V1 = volume of stock solution (initial) M2 = molarity of dilute solution V2 = volume of dilute solution

M1V1 = M2V2 How many milliliters of aqueous 2.00M MgSO4 solution must be diluted with water to prepare mL of aqueous 0.400M MgSO4? M1 = 2.00M MgSO4 M2 = 0.400M MgSO4 V2 = mL MgSO4 V1 = ?

M1V1 = M2V2 Solve for V1 V1 = M2 x V2 M1 0.400M x 100.00 mL 2.00M

M1V1 = M2V2 How many milliliters of a solution of 4.00M KI are needed to prepare L of 0.760M KI?