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Solutions Day 2 Chemistry Ms. Boon 11.28.12

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Catalyst Identify the following substances as homogeneous mixtures or heterogeneous mixtures: Milk Gasoline Muddy water Steel Coffee Ink Crude oil Bronze Brass seawater Objective Agenda Catalyst Homework review Percent concentration Exit slip I can express the concentration of a solution by percent concentration. HW: Read pp. 460-464, 468-470 Problems pp. 488 #4, 16, 21, 25

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Homework Review: pp. 459 3.The solvent is the substance in excess. There is more of it. The solute is the substance dissolved in the solvent. 4.(a) solvent: water; solute: carbon dioxide (b) solvent: water; solute: apple extract (c) solvent: water; solute: coffee filtrate (d) solvent: water; solute: salt 5.No. A solution is any homogeneous mixture and can be gas & gas or solid & solid. (example: air or brass) 12. Water is evaporating, leaving behind the solute which is salt.

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Solutions Mini-Review A solution is a homogeneous mixture. In a solution, the solute is distributed evenly throughout the solvent.

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Solutions Mini-Review Therefore, any part of a solution has the same ratio of solute to solvent as any other part of the solution. This ratio (or comparison) of solute to solvent is called concentration.

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Percent Concentration One way to express concentration is by using a percentage. Percentage concentration is the number of grams of solute per 100 grams of solution. % concentration = g solute___ x 100% g solution Example: Roundup weed killer is a solution containing 18% chemical pesticide. There are 18 g pesticide for every 100 g solution.

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Finding the Percent Concentration % concentration = g solute___ x 100% g solution The denominator is the mass of solution. Add: g solute + g solvent Example 1: What is the percentage by mass of a solution made by dissolving 0.5 g of glucose in 9.5 g of water?

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Finding the Percent Concentration % concentration = g solute___ x 100% g solution The denominator is the mass of solution. Add: g solute + g solvent Example 2: What is the percentage by mass of a solution containing 12.70 g of water and 0.49 g of potassium sulfate (K 2 SO 4 )?

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Finding the Percent Concentration % concentration = g solute___ x 100% g solution The denominator is the mass of solution. Add: g solute + g solvent Example 3: What is the percentage by mass of a salt water solution made by dissolving 0.5 mol NaCl in 500 g water? The units must be grams. If given moles, multiply by the molar mass.

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Finding the Percent Concentration % concentration = g solute___ x 100% g solution The denominator is the mass of solution. Add: g solute + g solvent Example 4: A student wants to make a 5.0% solution of rubidium chloride and water with 10.0 g rubidium chloride. How much water is needed? If given the %, work backwards to find the unknown mass.

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Exit Slip Show all your work and label your answer with the correct units. 1.A chemist dissolves 20 g silver nitrate in 180 g water. What is the percent concentration? 2.A glass of koolaid contains 4.0 g sucrose and 96 g water. What is the percent concentration? 3.A fish tank contains 4 mol NaCl (salt) and 1000 g water. What is the percent concentration?

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