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HASPI revised February 2011 Introduction

Typically, it is the pharmacist’s role to prepare a patient’s medication, whether that medication is in the form of a tablet or in the form of a solution. A solution is comprised of a solute and a solvent. A solute is a substance (often a solid or liquid) which has dissolved, or dissociated, within another substance. A solvent, which is also called a diluent in the healthcare field, is the substance or medium that is doing the dissolving. Whether a researcher has a career in biotechnology, in biomedical, or in clinical healthcare, he/she will likely at some point have to make their own molar solutions.

Making Molar Solutions

A 1 molar solution (1M) contains 1 mole of solute dissolved in 1 liter of solution. A mole of a solute is the molecular weight (molar mass) which is expressed in grams and can be found on the periodic table for each element. The

solvent is typically deionized (DI) water or saline water. Use the following to guide you through the process of making a 1M NaCl solution.

Problem: How much sodium chloride (NaCl) is needed to make 1 liter of an aqueous 1M solution?

Task Answer

Step 1: Calculate the molecular weight (molar mass) of sodium chloride (NaCl) by using the periodic table.

Be sure that your units are in g/mol.

Molecular Weight (molar mass) NaCl:

Step 2: You have been given the Erlenmeyer flask shown at the right. Label the amount of salt that you placed inside the flask to make 1M NaCl solution.

Then, use your pencil to shade in the amount of deionized (DI) water you will need to add in order to complete the solution.

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22.99 35.5

www.wikimedia.com Molecular Weight (molar mass) NaCl

:

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HASPI revised February 2011

Lab: The Bear Necessities

Introduction

Unfortunately, not every solution needs to be a 1M concentration and, sometimes, making a 1 liter solution will be too much volume for your needs. In the following procedure, you will be making 50-mL molar solutions and observing the effects on a gummy bear.

Objective: Students will be able to make molar solutions and analyze their tonicity.

Materials

6 plastic cups labeling pen 50-mL graduated cylinder balance

Deionized (DI) water 6 Gummy Bears 3 250-mL beakers weighing boat

Corn syrup stirring rod spatula sucrose

Procedure

1. Label your 6 plastic cups with a letter A, B, C, D, E or F and your group name.

2. Using the balance, weigh one gummy bear and record its mass in grams in the data table below Cup A and beside Mass of Gummy Bear (Day 1). Place this gummy bear in cup A. Weigh the second gummy bear and record its mass in grams in the data table and place it in cup B. Continue until you have weighed and recorded the mass of each gummy bear and placed 1 gummy bear into each cup.

3. Measure 50-mL of deionized water using the graduated cylinder and pour into cup A.

4. For Cup B, you will need to make 50-mL of 0.1M sucrose solution. First, find the molar mass of sucrose (C

12

H

22

O

11

) and write your answer in your data table below. Be sure to include your units (g/mol).

5. Your molar mass indicates the number of grams in 1 mole of sucrose. This is also the number of grams that you would dissolve in 1 liter of water for a 1M sucrose solution. How would you calculate the number of grams that you need for a 0.1M sucrose solution for a total volume of 50 mL? 0.1M is 0.1 moles per 1 liter of solution. So, take 0.1 times your molar mass and show your work in your data table. Now, that is the number of grams that you need for 1 L (or 1000mL). How many grams do you need for 50 mL? Show your work in the data table.

6. Add this number of grams of sucrose to a clean beaker. Add up to 50 mL with DI water and stir until the sucrose is completely dissolved. Pour into Cup B.

7. For Cup C, you will need to make 50-mL of 1M sucrose solution. Identify the molar mass of sucrose and write it in your data table. This is the number of grams of sucrose that you need for 1 L (1000 mL). How many grams do you need for 50 mL instead? Show your work in your data table.

8. Add this number of grams of sucrose to a clean beaker. Add up to 50 mL with DI water and stir until the sucrose is completely dissolved. Pour into Cup C.

9. For Cup D, you will need to make 50-mL of 2M sucrose solution. Identify the molar mass of sucrose and write it in your data table. 2M means that you will need 2 moles per liter of solution. Calculate how many grams 2 moles of sucrose would be by taking 2 times your molar mass and record in your data table. Now, this is the

www.scienceprojectideasforkids.com

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HASPI revised February 2011

number of grams that you need for 1L (1000mL). How many grams do you need for 50mL? Show your work in the data table.

10. Add this number of grams of sucrose to a clean beaker. Add up to 50 mL with DI water and stir until the sucrose is completely dissolved. Pour into cup D.

11. For Cup E, you will be adding 50-mL of corn syrup which has a concentration of 5M.

12. For Cup F, there will be no solution added.

13. Place your cups in a cool, safe place overnight.

14. On Day 2, make observations of your gummy bears in your data table. Then, using a balance, place one gummy bear in a weighing boat at a time and record its mass (g) in the data table below. Determine tonicity.

Cup A (0M)

Cup B (0.1M)

Cup C (1M)

Cup D (2M)

Cup E (5M)

Cup F (no M) Mass of

gummy bear (Day 1) Mass of gummy bear

(Day 2) Molar mass of

sucrose (C

12

H

22

O

11

)

NA NA

Step 1:

Calculating grams

NA

0.1 x molar mass= 1 x molar mass= 2 x molar mass=

NA NA

Step 2:

Converting to 50mL

NA NA NA

Observations/

Qualitative Data

Tonicity (hypotonic, hypertonic, or

isotonic?) Explain what

happened with each cup

in terms of

osmosis.

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HASPI revised February 2011

Introduction to IV fluids

There are two types of fluids that are used for intravenous (within vein) drips: crystalloids and colloids. Crystalloids are aqueous solutions of water-soluble mineral salts (saline) while colloids are solutions with insoluble particles (i.e. blood) Normal saline, the most commonly-used crystalloid fluid, is a solution of sodium chloride (NaCl) at 0.9% concentration which is close to the concentration in the blood (isotonic). A solution of 5% dextrose (glucose) in water, sometimes called D5W, is often used if the patient is at risk for having low blood sugar or high sodium. Ringer’s solution or Ringer’s lactate solution is also isotonic and used for large-volume fluid replacement As a healthcare

professional, it is essential to know what type of fluids to administer to a patient and how the solutions are made.

Making Intravenous solutions

1. Solutions for IV drips are often labeled as percent solution. As an example, normal saline is 0.9% sodium chloride. A bolus of 250mL-1000mL is typically used for treating dehydration or low blood pressure, since it can increase blood volume. What is the molarity of 0.9% normal saline?

Task Answer

Step 1:

0.9% = number of grams per 100 mL.

Rewrite in grams per 100 mL.

Step 2:

How many grams would you need for the same concentration in a 1000 mL (1L) volume?

Step 3:

Take your answer for Step 2 and divide it by the molar mass of NaCl. This gives you the number of moles in 1000 mL (1L).

Step 4:

What is the molarity of 0.9% normal

saline?

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HASPI revised February 2011

2. When diabetic patients experience low blood sugar, a 5% dextrose solution (D5W) may be administered. Dextrose is a form of glucose and is utilized by the body cells for basic metabolic needs (cell respiration). Using the molecular formula for glucose (C

6

H

12

O

6

), determine the molarity of this solution.

Task Answer

Step 1:

5% = number of grams per 100 mL.

Rewrite in grams per 100 mL.

Step 2:

How many grams would you need for the same concentration in a 1000 mL (1L) volume?

Step 3:

Take your answer for Step 2 and divide it by the molar mass of glucose. This gives you the number of moles in 1000 mL (1L).

Step 4:

What is the molarity of 5% dextrose solution?

3. Magnesium sulfate, or “mag,” is administered to women who are experiencing preterm labor or pre-eclampsia (pregnancy-induced high blood pressure). Magnesium sulfate (MgSO

4

) is thought to slow uterine contractions by blocking the release of calcium to uterine muscles as well as prevent seizures in pre-eclampsia patients. If a bolus of 50% magnesium sulfate solution is ordered, what would be the molarity of the solution?

Task Answer

Step 1:

50% = number of grams per 100 mL.

Rewrite in grams per 100 mL.

Step 2:

How many grams would you need for the same concentration in a 1000 mL (1L) volume?

Step 3:

Take your answer for Step 2 and divide it by the molar mass of magnesium sulfate. This gives you the number of moles in 1000 mL (1L).

Step 4:

What is the molarity of 50% “mag”

solution?

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4. Lactated Ringer’s solution contains electrolytes, such as sodium lactate, potassium chloride, sodium chloride, calcium chloride and water, and is usually given in combination with 5% dextrose solution (D5W). Patients who are severely dehydrated due to flu or hardship are given an infusion of 1000 mL of lactated Ringer’s solution with continuous blood level monitoring. Lactated Ringer’s solution is an isotonic solution of approximately 0.9% solute concentration. Why is pure water (0% solute concentration) often a poor choice to treat patients who need hydration? Use tonicity, cells, and electrolyte imbalance in your answer.

IV Flow Rate: Problems with Fluid Balance and Concentration

5. Fluid overload occurs when fluids are given at a higher rate or in a larger volume than the system can absorb or excrete. Consequences may include hypertension, heart failure, and pulmonary edema. Pharmacologists assist physicians in determining the drip rate for patients which is the number of drops per minute to be infused (gtt/min). Drip factor is found on the label and is given in drips per milliliter (gtt/mL). Below is an example.

Formula for IV Flow Rate:

volume (mL)/time (min) x drip factor =drip rate(gtt/min)

The ER physician orders IV fluids to hydrate a client. The order is written as "D5NS 4 Liters over 24 hours." Looking at the package indicates the drip factor of the tubing is 15 gtt/ml. What is the drip rate?