Solutions

Solutions

By Mihir Paranjape

Solution

• Homogeneous mixture of two or more substances.

• Solute: Substance that dissolves.

• Solvent: Substance that does the dissolving.

• A DILUTE solution contains small amount of Solute.

• A CONCENTRATED solution contains large amount of Solute.

Rate of Dissolution

To increase the Rate of Dissolution of a Solid Solute,

• Increase Temperature

• Increase Mixing (Agitation)

• Like dissolves like. Polar (water) dissolves ionic and polar solutes.

• Increase Surface Area (powder dissolves faster).

Multiple Choice

What is a substance that is dissolved in another substance? 

• solution
• solute
• solvent
• compound

Multiple Choice

Another name for a homogeneous mixture is 

• an element.
• a solution.
• a compound.

Multiple Choice

Kool-Aid - Powder, sugar, and water
Identify the solvent 

• water
• powder
• sugar
• powder and sugar

Rate of Dissolution

To increase the Rate of Dissolution of a Solid Solute,

• Increase Temperature

• Increase Mixing (Agitation)

• Like dissolves like. Polar (water) dissolves ionic and polar solutes.

• Increase Surface Area (powder dissolves faster).

Multiple Choice

Which of the following actions will NOT

increase the rate of dissolution

(dissolving)?

• Stirring the solution

• Decreasing the temperature

• Increasing the surface area of the

  solute

• Increasing the temperature

Multiple Choice

The concentration of a mixture can be increased in which of the following ways?

• Heating the mixture
• Adding more water “solvent”
• Adding more powder “solute”
• Stirring the mixture

Types of Solutions

Unsaturated: More Solute can be dissolved.

Saturated: ​No More Solute can be dissolved at a given temperature.

Super Saturated: ​More Solute is dissolved than under normal conditions.

Multiple Choice

When a certain amount of solvent cannot hold any more solute it is called a ________ solution.

• Diluted
• Saturated

Multiple Choice

How does a solution become supersaturated?

• dissolve lots of solvent in it.
• dissolve a little solute in it. 
• dissolve more solute than you should be able to. 
• dissolve a super amount of solvent in it. 

Molarity

Molarity is a way of measuring the concentration of a solution.

Remember moles = g of solute / Molar Mass of Solute.

You can also use the Molarity Triangle to calculate different values.

Always written in M.​

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Molarity

Find the Molarity of a solution of 100 g NaCl in 100 mL of water.

​Solute: NaCl Solvent: Water

Molar Mass NaCl = 58.5 g/mol.

Moles of NaCl = 100/58.5 = 1.71 moles

Liters of Solution = 100 mL / 1000 mL = 0.1​

M = 1.71​/0.1 = 17.1 M

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Molarity

Find the amount of NaCl in 100 mL of water to make a 6 M solution.

​Solute: NaCl Solvent: Water

Molarity = 6M

Liters of Solution = 100 mL/1000 mL = 0.1 L

Calculate moles = Molarity x Liters = 6 x 0.1 = 0.6 moles

Convert moles to g

g NaCl = moles x Molar Mass = 0.6 x 58.5 = 35.1 g​

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Molarity

To make a 5M solution of NaCl, how much water should we add to 60 g of NaCl?

​Solute: NaCl Solvent: Water

moles of NaCl = g/MM = 60/58.5 = 1.026 moles​

Molarity = 5M

Liters of Solution = ?

Liters = moles / Molarity​ = 1.026/5 = 0.205 L

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Multiple Choice

What is the molarity of 1 mole of Ba+ in 2 L of water

• 1 M
• 2 M
• .5 M
• .25 M

Multiple Choice

What is the molarity of 3 mole of hydrochloric acid in 3 L of water. 

• 3
• 1
• 6
• 9

Multiple Choice

Molarity is measured in

• moles per kg
• mols per L
• moles per kJ
• moles per mL

Multiple Choice

How many moles are needed to make 2.5 L of a 3.8 M solution? 

• 9.5 mol
• 0.66 mol
• 1.5 mol
• 15 mol

Dilution

Sometimes we have to dilute or add more solvent to a given concentration to make a lower concentration. This is called Dilution.

Generally M1 and V1 are the Molarity and Volume of the concentrated solution while M2 and V2 are the diluted solution.

So if you know three of these, you can solve for the remaining one.​

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Dilution Problem

How many mL of 0.1 M HCl can you make from 100 mL of 10M HCl solution.

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In this case, the concentrated solution has: M1 = 10 M, V1 = 100 mL

​Diluted solution has: ​M2 = 0.1 M, V2 = ?

Plugging in

10 x 100 = 0.1 x V2

1000 = 0.1 x V2

V2 = 1000/0.1 = 10,000 mL or 10 L.​

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Dilution Problem

How much of a 10M solution would you need to make 1000 mL of 1M solution?

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In this case, the concentrated solution has: M1 = 10 M, V1 = ? mL

​Diluted solution has: ​M2 = 1 M, V2 = 1000 mL

Plugging in

10 x V1 = 1 x 1000

10 x V1 = 1000

V1 = 1000/10 = 100 mL

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Multiple Choice

What is the molarity of a solution made by diluting 26.5 mL of 6.00M HNO₃ to a volume of 250 mL?

• 15.9 M
• 0.636 M
• 0.642 M
• 1.59 M

Multiple Choice

How many mL of stock solution of 2M NaCl do you need to prepare 100 mL of 0.150M NaCl?

• 7.5 mL

• 15 mL

• 1333 mL

• 200 mL

Multiple Choice

How many mL of 10.8M HCl are required to make 100.0 mL of 3.00M acid?

• 27.8 mL

• .278 mL

• 2.8 mL

• 278 mL