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Chemistry 11 Introduction to Molarity Lesson 1. Chemists need to make solutions that have precise concentrations. Pesticides must be in proper concentrations. Food additives must be in correct concentrations. A driver is legally impaired at 0.08 mg/mL blood alcohol content.
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Chemistry 11 Introduction to Molarity Lesson 1
Chemists need to make solutions that have precise concentrations
Pesticides must be in proper concentrations. Food additives must be in correct concentrations. A driver is legally impaired at 0.08 mg/mL blood alcohol content. A new driver is legally impaired at 0.00 mg/mL blood alcohol content. Chemists control the concentration of chemicals using the concepts we will develop in this unit.
The concentration of a solution tells you how much solute that is dissolved in a given amount of solvent (water). The molarity is the concentration of a solution. Moles Molarity = Litre
1. 2.255 molesof NaCl is dissolved in 4.0 Lof water, calculate the molarity. Molarity = 2.255 moles 4.0 L = 0.56 moles/litre = 0.56 M(Molar) Mmeans moles per 1litre
2.5.00 g KOHis dissolved in 250. mLof water, calculate the molarity. 5.00 g x 1 mole 56.11 g Molarity = 0.250 L =0.356 M
3. How many gramsare there in 205. mLof a 0.172 Msolution of NaCl? 0.205 L x 0.172 moles x 58.5 g = 2.06 g 1 L 1 mole
4.How many litres of 0.500 M MgCl2solution contain 125 gMgCl2? 125 g x 1 mole x 1L = 2.62 L 95.3 g 0.500 mole
5. How many gramsof NaCl must be used to prepare a 100.0 mLof0.250 Msolution. 0.1000 L x 0.250 moles x 58.5 g =1.46 g 1 L 1 mole
6. How many millilitres of a 0.200 Msolution of CoCl2will contain 25.0 g? 25.0 g x 1 mole x 1 L x 1000 mL = 962 mL 129.9 g 0.200 mol 1 L
7. Describe how you would prepare 100.0 mLof a0.200 Msolution of CoCl2. 0.1000 L x 0.200 moles x 129.9 g = 2.60 g 1 L 1 mole Weigh 2.60 g of CoCl2 Dissolve in water Transfer and rinse to a 100 mL volumetric flask- fill to the line