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   CE 170: Water Quality and Supply Engineering

Lab 1: Lab Safety and Concentration Units

 

Laboratory Course Guidelines:

 

1. There will be 13 lab write-ups worth 20 points each. In addition, two quizzes, each worth three lab write-ups, are scheduled. As stated in lecture, attendance at all 15 lab sections and completion of all write-ups are required for a passing grade in the class.

 

2. Lab write-ups are due at the beginning of the following lab unless the instructor directs otherwise. Late submittals will be assessed a 5-point penalty (out of 20) for up to one week after the due date. Labs turned in later than one week late will receive a "0" grade. Note that all labs write-ups must be turned in to pass the course, even if they aren't worth any points.

 

3. The format of the lab write-ups (e.g., layout, tables, graphing) will be governed by the guidelines for homework preparation distributed in class. In particular, note that most lab write-ups must include samples of every major type of calculation performed. This requirement holds even if a spreadsheet is used to perform the lab calculations.

 

4. You will be working in groups of two or three, and in most cases turning in group write-ups. It is expected that all members of a lab group participate fully in the performance and preparation of each lab.

 

5. Unless otherwise instructed, you will be expected to stay for the full scheduled duration of the lab. If you finish collecting your data early, use the remaining time to start your write-up.

 

6. At the end of each lab session, please wash your glassware, put away equipment in designated places, and clean up your lab space.

 

Lab Safety Guidelines:

 

1. Professional decorum is required at all times. This includes following the procedures in the written handouts and those provided by the instructor.

 

2. Open-toed shoes are not allowed at any time.

 

3. Food and drink are not allowed in lab.

 

4. Protective wear (eyewear, gloves, and/or lab coats) are to be worn whenever directed by the instructor.

 

5. The instructor has the right and obligation to ask you to leave whenever you are not acting in a safe manner, or are not properly equipped.

 

 

Background Material on Concentration Units

 

Concentration Units:

 

1. Molar concentrations are used whenever a chemical reaction is involved. Units are:

 

 

In natural systems, millimolar (mM) concentration predominate.

 

2. Mass concentration is used when physical measurements are made. The units are:

3. Conversion between molar and mass concentrations is made using molecular weight. Just watch the units! An example is: Convert a 94.06 mg/L solution of sodium bicarbonate (NaHCO3 - MW = 84.01 g/mole) to a molar concentration.

4. Normal concentrations are typically used whenever a chemical reaction involving an acid or base is described. The analog to a mole in normal concentrations is the equivalent. In the context of acid-base reactions, "an equivalent is a quantity of substance that will liberate or react with one mole of hydrogen ions." The equivalent number is the number of hydrogen (H+) ions furnished or needed in a neutralization reaction. Therefore, the equivalent weight is the molecular weight divided by the equivalent number. Normality is then defined as:

 

 

Consider the following table:

 

Molecular and equivalent weights of representative bases and acids.

 

 

Compound

 

 

Reaction

Molecular

Weight

(g/mole)

Equivalent

Number

(eq/mole)

Equivalent

Weight

(g/eq)

HNO3

63.01

1

63.01

H2SO4

98.07

2

49.04

NaOH

40.00

1

40.00

Ca(OH)2

74.09

2

37.05

 

 

5. Conversion between molar and normal concentration is made using equivalent number. An example is: Convert a 0.25 M solution of sulfuric acid to a normal concentration.

 

6. Conversion between normal and mass concentration is made using equivalent weight. An example is: Convert a 0.5 N H2SO4 solution to a mass-based concentration.