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Unit 5 Mole.

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Presentation on theme: "Unit 5 Mole."— Presentation transcript:

1 Unit 5 Mole

2 You will understand the concept of mole if you understand the concept of a dozen
1 dozen chairs=12 chairs 1 mole=6.022∙1023= = (we always use scientific notation) 1 mole of atoms of Na=6.022∙1023 atoms of Na 1 mole of molecules of H2O=6.022∙1023 molecules of H2O

3 The mole is used to count atoms and molecules.
The mass of 1 mole of atoms is the same number in grams as the mass of 1 atom in u. For example: 1 atom of Na has a mass of 23 u 1 mole of Na has a mass of 23 g 1 molecule of H2O has a mass of 18 u (1∙2+16). 1 mole of molecules of H2O has a mass of 18 g.

4 Exercises 1. How many atoms are there in 4 moles of Ca?
2. How many moles are there in 3.063∙ atoms of Fe? 3. How many molecules are there in 7.3 moles of NH3? And how many atoms of N and H? 4. How many moles are there in 9.1∙ molecules of O2? And how many atoms of O? And how many moles of atoms of O?

5 Exercises 5. How many moles are there in 5.1 g of Ni?
6. How many moles are there in 20 g of Ca(OH)2? And how many moles of Ca, O and H? 7. What will be the mass of 8 moles of Cu? 8. What will be the mass of 9.3 moles of CaSO4?

6 Do you remember from the past term the different ways to express the concentration of a solution? mass%=(mass solute/mass solution)·100 volume%=(volume solute/volume solution)·100 C (g/L)=mass solute (g)/volume solution (L)

7 Now that you know what a mole is, you can learn a new way of expressing the concentration of a solution: the molarity (also called molar concentration). M=number of moles of the solute/volume of the solution in L In Spanish: molarity=molaridad molar concentration=concentración molar

8 Exercises 9. We dissolve 21 g of sodium chloride (NaCl) in water, until the final volume of the solution is 0.5 L. Calculate the molarity of the solution Calculate the mass of sodium sulfate (Na2SO4) there is in 250 mL of a solution 1 M of this compound We dissolve 14 g of potassium chloride (KCl) in water, until the final volume of the solution is 250 mL. a) Calculate the molarity of KCl in this solution. b) Calculate the mass of KCl there is in 100 mL of this solution. c) Calculate the volume you need to take of this solution in order to have 2 g of KCl.


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