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**Mixtures, solutions, and solubility**

Exploring non-pure substances

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**Review: what is a mixture?**

Mixtures are physical combinations of substances Mixtures can be separated into their original components Mixtures can be evenly distributed (homogenous) or unevenly distributed (heterogeneous).

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**Review: what is a mixture?**

Which of the two options below is a homogenous mixture? Which is a heterogeneous one?

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**Review: what are solutions?**

Solutions are homogeneous mixtures in which one part of the solution is dissolved into the other. Solute: part that dissolves; present in smaller amount Solvent: part that is dissolved into; present in larger amount Both the solute and the solvent can be in any of the three states/phases of matter; however, we usually only discuss liquid solvents.

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**Review: what are solutions?**

Think back to the ethanol and water mixture. Which is the solute and which is the solvent?

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**Review: what are solutions?**

The ethanol was present in a smaller amount, making it the solute. The water was present in a greater amount, making it the solvent.

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What is solubility? Solubility is a measure of how well a particular solute dissolves in a particular solvent; it is the ability to form a solution solution + ability solubility Therefore, it is defined as a property of the solute. Solubility can be effected by several factors, some of which we will explore in the near future.

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What is saturation? Saturation is a relative measure (qualitative) of how much of a solute is dissolved compared to the maximum amount allowed (based on solubility). A saturated solution contains exactly that maximum amount dissolved in solution An unsaturated solution contains less than the maximum amount A supersaturated solution contains more than the maximum amount

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What is saturation?

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Concentration

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What is concentration? Concentration is a quantitative measure of how much (mass) solute is dissolved in an amount (volume) of solvent The units are the same as those for density: g/mL or g/cm3 General Formula = mass of solute dissolved / volume of solvent Usually reported in g / 100 mL of solvent

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**Density v concentration**

What is density a measure of?

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**Density v concentration**

What is concentration a measure of?

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**How to calculate concentration**

What is the concentration of a solution if 15 g of sugar is dissolved in 50 cm3 of water? What is the concentration in g/100 cm3?

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**How to calculate concentration**

What is the concentration of a solution if 15 g of sugar is dissolved in 50 cm3 of water? Ans – 0.30 g/cm3 What is the concentration in g/100 cm3? Ans – 30 g/100 cm3

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**How to calculate concentration**

If the concentration of a solution is 2.53 g/mL, how many grams of solute are dissolved in 75 mL of water?

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**How to calculate concentration**

If the concentration of a solution is 2.53 g/mL, how many grams of solute are dissolved in 75 mL of water? Ans – 190 g of solute

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**Concentration Practice #1**

1) What is the concentration of a solution composed of 8.21 g of potassium chromate dissolved in enough water to make 500 mL of solution 2) If you had g of silver nitrate and wanted to make a solution with a concentration of g/mL, how much water would you need? 3) How many grams of sugar must be added to 450 mL of water to make a solution with a concentration of 0.12 g/mL?

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**Concentration practice #2**

1) What is the concentration if 75.0 g of ethanol are dissolved in 0.5 L of water? What is this concentration in g/100mL? 2) If you wanted to make 1000mL of a 6.0 g/mL solution of citric acid, how many grams must of citric acid must you add? 3) Determine the concentration of a solution that contains lbs of salt and 300 mL of water. (Note that 1 lb = g)

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Bonus: another unit Another way of expressing concentration is by percent. General formula = g of solute / 100 g of solvent Example: A solution of 45 g of table salt in 100 mL of water (density = 1.0 g/mL) is a 45% solution.

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**Concentration practice #3**

1) What is the percent concentration of a solution made using 43 g of sugar dissolved in 475 mL of water (density = 1.0 g/mL)? 2) How many grams of potassium permanganate would you need to add to 1 L of water to make a solution with a concentration of 20%? 3) What is the percent concentration of a solution made using 100 g of caffeine dissolved in 800 mL of ethanol (density = 0.80 g/mL)?

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