1.5 Solutions

Starter Moles How many moles are in 45g of NH 4 Cl

Objectives To KNOW the terms SOLVENT, SOLUTE, SOLUTION, CONCENTRATION To BE ABLE TO calculate the concentration of solutions. To UNDERSTAND when solutions are more or less concentrated and explain why.

A solution is a homogeneous mixture of 2 or more substances. It is made of a solvent and a solute.

SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) SOLVENT – the part of a solution that dissolves the solute (usually the greater amount) Solute + Solvent = Solution SoluteSolventExample solidsolid Metal alloys solidliquid Kool aid liquidliquid Alcoholic drinks gasliquidPepsi gasgasair

What is Concentration? It is a measure of how many SOLUTE particles there are in a SOLVENT. There more particles there are the more concentrated the SOLUTION is.

Concentration of Solute The amount of solute in a solution is given by its concentration. Molarity (M) = moles solute (moles) volume of solution (dm 3 )

Concentration If something is concentrated it has more moles/grams of solute per amount of solvent. Ex: 12 M HCl If something is dilute it has less moles/grams of solute per amount of solvent Ex: 0.10 M HCl

Questions Calculate the concentration of the solution formed when 4.00 moles of glucose are dissolved in 5.00 dm -3 If 2.00g of sodium hydroxide is dissolved in 200 cm 3 of water, determine the concentration of the resulting solution. What mass of hydrated copper (II) sulphate crystals is present in 17.3 cm 3 of a mol dm -3 solution of copper(II)sulphate.

PROBLEM: Dissolve g of NaCl in water to make 500cm 3 of solution. Calculate the Molarity. Step 1: Calculate moles of NaCl Step 2: Calculate Molarity [NaCl] = 0.34 M m=n x M 10 = n x 58.5 n = 0.17 moles C = n/V C =0.17/0.5 C=0.34 molesdm -3

PROBLEM: Dissolve 5.00 g of NiCl 2 6 H 2 O in enough water to make 250 mL of solution. Calculate the Molarity. Step 1: Calculate moles of NiCl 2 6H 2 O Step 2: Calculate Molarity NiCl 2 6 H 2 O [NiCl 2 6 H 2 O ] = M

Practice Questions Calculate the concentration of the following: 6g LiOH in 250cm 3 of water 4g Mg(NO 3 ) 2 in 2dm 3 of water 3.8g of C2H5OH in 500cm 3 of acetone. 5.5g Calcium sulphate in 200cm 3 of water. 1kg Magnesium carbonate in 10dm 3 of water.

Step 1: Change cm 3 to dm mL * 1 dm 3 /1000cm 3 = dm 3 Step 2: Calculate. Moles = ( mol/ dm 3 ) (0.250 dm 3 ) = moles Step 3: Convert moles to grams. ( mol)(90.00 g mol -1 ) = 1.13 g moles = MV What mass of oxalic acid, H 2 C 2 O 4, is required to make 250 mL of a M solution?

IB Note Square brackets [0.60] means 0.60 M or 0.60 mol/L or 0.60 mol dm -3 This is what IB uses! Note: Can Also use g dm -3 (g/dm 3 ) Is the number of grams of solute dissolved per dm 3 of solution

Questions Calculate the volume to which 20cm -3 of 7.63 mol dm -3 hydrochloric acid must be diluted to produce a solution with a concentration of exactly 5.00 mol dm -3

Calculate the amount of hydrochloric acid (in mol) present in cm 3 of mol dm -3 HCl(aq)?

Molarity = mol dm -3 so Molarity x dm 3 = mol mol = mol dm -3 x dm -3 = mol HCl grams = mol x g mol -1 =.0862 g HCl

What volume of a 1.25 mol dm -3 potassium permanganate solution, KMnO 4 (aq), contains 28.6 grams KMnO 4 ?

Molarity = mol dm -3 so dm -3 = mol/Molarity mol = 28.6 g / g mol -1 =.181 mol dm -3 =.181 mol/1.25 mol dm -3 =.145 dm 3

What will be the concentration of the solution formed by mixing 200 cm 3 of 3.00 mol dm -3 HCl(aq) with 300 cm 3 of 1.50 mol dm -3 HCl(aq)?

Find total moles.200 dm -3 x 3.00 mol dm -3 =.600 mol HCl.300 dm -3 x 1.50 mol dm -3 =.450 mol HCl Total moles = mol Find total volume:.200 dm dm 3 =.500 dm 3 Concentration: mol/.500 dm 3 = 2.10 mol dm -3

Terms to Know Molar mass Mole Avogadro’s constant Chemical equation Molar ratio Solute Solvent Solution Concentration