CHEM 120 Unit 3, Lab - Laboratory 4; Solution Chemistry

$15.00

Institution	Chamberlain
Contributor	Karin Austin

Description

Learning Objectives:

To learn how to prepare solutions of specific concentrations
To learn about molarity, % concentration, and osmolarity.

In this lab, we will learn how to calculate solution concentration and prepare solutions. For a given solution, different ways of expressing concentration are used depending on our purposes. Solutions made of the same substances but at different concentrations can have very different properties. For example, an animal cell placed in a 0.1% NaCl solution will swell, the same cell placed in a 10% NaCl solution will shrivel or crenate. A good understanding of solution concentration is vital to the understanding of many natural and synthetic processes.

Read the lab before coming to class. The expectation at Chamberlain (CCN/CU) is that you come to class fully prepared for lab.
Always dress properly for lab. Be sure to wear closed toed shoes and long pants to lab. In lab, wear your safety equipment including goggles, lab coat, and gloves.
Always check with your instructor regarding proper waste disposal.
Listen carefully to the professor’s instructions and work safely.
Always follow the rules outlined in the safety contract.
If in doubt of how to use a piece of lab equipment, ask you instructor. Improper use of lab equipment can be dangerous or could damage lab materials.
If you have any safety concerns, see your instructor.
Use deionized water (DI water) in your experiments.

Exploration 1: molarity

In this first exploration, we will be exploring molarity as we prepare solutions. As a reminder, molarity has units of mol/L.

Materials: NaCl, CaCl₂, DI water, 100ml beaker, 250 ml beaker, stirring rod

NaCl solution- method:

CaCl₂ solution- method:

Calculations:

Calculate moles of NaCl.
Calculate the molarity of your prepared NaCl solution.
If you used 50 ml of water instead of 100 ml of water to dissolve your NaCl, what would be the molarity of the solution?

Exploration 2: Dilutions

Materials: 1M NaCl solution from Exploration 1, DI water, 2 x 50 ml Erlenmeyer flasks (labeled A and B, respectively), and a 50 ml graduated cylinder.

NaCl serial solution dilution method:

Calculations:

Questions:

Which solution has the greatest number of NaCl molecules/ml of solution?
If you wanted to prepare a 50ml solution of 0.05 mM NaCl solution from NaCl and water, what mass of NaCl would you need to measure out? (note: 1000 mM = 1 M).
How many ml of a 1 M NaCl solution would you need to prepare 50 ml a 0.05mM NaCl solution? Show all work below ? (note: 1000 mM = 1 M)
Consider the two methods of preparing a 0.05 M NaCl solution from the questions above. Which would allow for a more accurate and simple preparation of the 0.05 M NaCl solution? Why?

Exploration 3: Osmolarity

Materials: 1M NaCl solution from Exploration 1, conductivity meter, DI water bottle, and a waste beaker.

Method:

Questions:

Which of the 0.05 M solutions have a greater Osmolarity and conductivity values? What do you think causes these higher values?
If a person’s blood had a high osmolarity value, what might this indicate?
1 molar solutions of LiCl, CaCl₂, and Na₃P are prepared. Arrange these in order from highest osmolarity value to lowest and explain why you decided on this order.

Reflection:

Reflect on 4 key concepts that you learned in this lab exercise. Be specific in your answer (this should require 10-14 sentences).