Molarity Revised 2011

Transcription

1 Molarity Revised 2011

2 Molarity Is the number of moles of solute dissolved in one liter of solution. The unit is moles/l Specifically, moles of solute/liter of solution. Rather than writing out moles per liter, it is abbreviated as M.

3 Formula for Molarity

4 Example 1: What is the Molarity of a 3L solution containing 5 moles of NaOH? M = M = M = Moles liter of solution 5.00 moles 3 liters of solution 1.67 moles/liter

5 Example 2 :What is the Molarity of a 10L solution containing 5 moles of Na 2 CO 3? M = M = M = Moles liter of solution 5.00 moles 10 liters of solution.5 moles/liter

6 Question #1 What is the molarity of a solution containing 4.67 moles of Li 2 SO 3 dissolved to make 2.04 liters of solution.

7 Question #1 What is the molarity of a solution containing 4.67 moles of Li 2 SO 3 dissolved to make 2.04 liters of solution. 4.67moles/2.04 L = 2.29 M

8 Question #2 What is the molarity of a solution containing moles of Al 2 O 3 to make 1.5 liters of solution.

9 Question #2 What is the molarity of a solution containing moles of Al 2 O 3 to make 1.5 liters of solution moles/1.5L = 0.42 M

10 Question #3 What is the molarity of a solution containing 8 moles of EDTA to make 7.56 liters of solution

11 Question #3 What is the molarity of a solution containing 8 moles of EDTA to make 7.56 liters of solution 8.00 moles/ 7.56L = 1.06 M

12 We can also determine the moles of solute in a solution if we know the volume and the molarity.

13 Example 3: How many moles of Na 2 CO 3 are there in 10 L of 2 M solution? moles = liter of solution x Molarity moles = 10 L x 2 M moles = 20

14 Example 4: How many moles of Cu(NO 3 ) 2 are in 3.35 liters of a 2 M Cu(NO 3 ) 2 solution? moles = liter of solution x Molarity moles = 3.35 L x 2 M moles = 6.7

15 Question #4 How many moles of NaCl are contained in 100 ml of a 0.2 M solution?

16 Question #4 How many moles of NaCl are contained in 100 ml of a 0.2 M solution? 100 ml (convert) 0.1 L moles = liter of solution x Molarity moles = 0.1 L x 0.20M =.02 moles

17 Question #5 How many moles of Cu(NO 3 ) 2 are contained in 2.35 liters of a 2 M solution?

18 Question #5 How many moles of Cu(NO 3 ) 2 are contained in 2.35 liters of a 2 M solution? moles = liter of solution x Molarity moles = 2.35 L x 2 M = 4.7 moles

19 Questions #6 How many moles of Pb(NO 3 ) 2 are contained in 160 ml of a Molar solution?

20 Questions #6 How many moles of Pb(NO 3 ) 2 are contained in 160 ml of a Molar solution? 160 ml (convert) 0.16 L moles = liter of solution x Molarity moles = 0.16 L x M =.07 moles

21 We can also determine the number of liters of a solution to use if we know the number of moles needed and the Molarity of the solution.

22 Example 6: What volume (in ml) of 18 M H 2 SO 4 is needed to contain 2.45 moles H 2 SO 4? liters of solution = moles of solute Molarity liters of solution = 2.45moles 18.0 M liters of solution =.136 = 136 ml

23 Question #7 What will be the final volume of a solution containing 4.67 moles of Li 2 SO 3 dissolved to make a 3.89 M solution?

24 Question #7 What will be the final volume of a solution containing 4.67 moles of Li 2 SO 3 dissolved to make a 3.89 M solution? Liters = Moles Molarity Liters = 4.67 moles 3.89 M Liters = 1.20 L

25 Question #8 What will be the final volume of a solution containing moles of Al 2 O 3 to make a 0.5 M solution?

26 Question #8 What will be the final volume of a solution containing moles of Al 2 O 3 to make a 0.5 M solution? Liters = Moles Molarity Liters = moles.5 M Liters = 9.81 L

27 You should remember from last time how to calculate the moles of solute. We can substitute Moles with the following liter of solution = g solute molar mass Molarity

28 Example 7: What will be the final volume of a solution containing 45.7 g of NaOH to make a.5 M solution? liters of solution = g solute molar mass Molarity liters of solution = 45.7 g g/mole 0.50 M liters of solution = 2.29 L

29 Question #9 What will be the final volume of a solution containing grams of Na 2 CO 3 to make a 34.8 M solution?

30 Question #9 What will be the final volume of a solution containing grams of Na 2 CO 3 to make a 34.8 M solution? Liters = g solute molar mass Molarity Liters = g g/mole 0.5 M Liters =.0073 moles 0.5 M Liters = 2.12 x 10-4 ( ) L

31 Question #10 What will be the final volume of a solution containing 48 grams of PbCl 2 to form a 5 Molar solution?

32 Question #10 What will be the final volume of a solution containing 48 grams of PbCl 2 to form a 5 Molar solution? Liters = g solute molar mass Molarity Liters = 48 g g/mole 5 M Liters =.172 moles 5 M Liters =.03 L

33 Molarity We can also determine the molarity of a solution if we know the number of grams and the volume of the solution. M= grams of solute molar mass liter of solution

34 Example 8: What is the Molarity of a 3 L solution containing 5 g of NaOH? M= grams of solute molar mass liter of solution M= 5 grams g/mole 3 liters of solution M=.042 moles/liter

35 Question #11 Sea water contains roughly 28 g of NaCl per liter. What is the molarity of sodium chloride in sea water?

36 Question #11 Sea water contains roughly 28 g of NaCl per liter. What is the molarity of sodium chloride in sea water? M= grams of solute molar mass liter of solution M= 28 g g/mole 1 liter of solution M=.479 moles M=.48 M 1 liter

37 Rearranging the equation above we can easily calculate the amount of chemical needed in grams for a solution of a given final volume and Molarity.

38 Example 9: How many grams of Cu(NO 3 ) 2 are needed to make liters of a 0.03 M Cu(NO 3 ) 2 solution? Grams = M x molar mass x liter of solution Grams = 0.03 moles/liter x g/mole x liters Grams = 1.63

39 Question #12 How many grams of Pb(NO 3 ) 2 are needed to make 16 ml of a 5.9 M Pb(NO 3 ) 2 solution?

40 Question #12 How many grams of Pb(NO 3 ) 2 are needed to make 16 ml of a 5.9 M Pb(NO 3 ) 2 solution? 16 ml (convert) L Grams = M x molar mass x Liter of solution Grams = 5.90 moles/liter x g/mole x Liters Grams = 31.27