Reagent Problems

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University of Miami *

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Course

151

Subject

Chemistry

Date

Dec 6, 2023

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pdf

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3

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BIL 151 - General Biology Laboratory Reagents and Concentrations: Practice Problems Using the formulas you learned from the “ Mixing Reagents and Calculating Concentrations ” document in your online lab manual, solve the following ten problems. Show your work in the space below each question. Each problem is worth one point. Submit the completed problems to your instructor before you leave lab today. Problem #1 You wish to make 500mL of 0.75M NaCl solution. How many g of NaCl must you add to 500mL of water to make a 0.75M solution? Answer( .500L ) x ( 0.75mol ) x ( 58.4 grams/mol ) = 21.9 g of NaCl Problem #2 You wish to make 1000mL of 3.0M KCl (potassium chloride) solution. How many g of KCl must you add to 1.0L of water to make a 3.0M solution? Answer: ( 1L ) x ( 3mol ) x ( 58.4 grams/mol ) =223.65g of NaCl Problem #3 How many g of sodium phosphate (Na 3 PO 4 ) must you add to 0.5L of solution to make a 0.04M sodium phosphate solution? Ty
Answer: ( .5L ) x ( .04mol ) x ( 163.94g/mol ) =3.28 g of Na 3 PO 4 Problem #4 You have added 526.42g of citric acid (C 6 H 8 O 7 ) to 2L of distilled water. What is the molarity of this solution? (HINT: You might need to rearrange things.) Answer: (2L) x (1.37mol) x (192.124g/mol) = 526.42 g of citric acid Problem #5 How many liters of distilled water must you add to 12.036g of magnesium sulfate (MgSO 4 ) in order to make a 0.200M solution of magnesium sulfate? Answer: (.05L) x ( .2 mol ) x (120.37g/mol) = 12.036 g of MgSO 4 Problem #6 How many L of 1M NaCl are needed to make 20mL of 0.8M NaCl/experimental solution? .016L Problem #7 In the previous problem, you calculated how many mL of 1M NaCl you need to make 20 mL of 0.8M NaCl solution. How many mL of distilled water must you add to the 1M volume you calculated in order to get a ]inal volume of 20mL?
4mL Problem #8 If you have 100mL of 10% hydrogen peroxide (H 2 O 2 ) and wish to bring the concentration to 3%, what will be the ]inal volume of your 3% H 2 O 2 solution? 0.33L Problem #9 How much water must you add to the starting volume of 100mL of 10% H 2 O 2 in the previous question to get a ]inal concentration of 3% H 2 O 2 ? 0.23L Problem #10 How much distilled water must you add to a 0.35M sodium phosphate solution to make 100mL of 0.5M sodium phosphate? None, you cannot add water to a solution in order to make it more concentrated.
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