Lab Practical Study Guide

The lab practical is an open book, open note exam taken in lab individually. With access to chemicals, reagents, glassware, and other lab equipment, you will be asked to identify unknowns, name compounds and write balanced equations associated with chemical reactions you perform while collecting observations. In this way, the practical tests your ability to communicate effectively, work safely, and draw conclusions from using the basic chemistry we have explored this semester.

The topics below outline the focus of the lab practical.

Lab Safety & Standard Operating Procedures:

Be sure to wear safety at all times while working in a laboratory or while others are working around you
Practice proper small scale technique:

Carry multiple pipettes in a well tray for safety and to avoid risk of contamination
Allow drops to fall a small distant through the air (to avoid contamination) at a 90^o angle relative to the plastic reaction surface (to maintain reproducibility)
Proper waste disposal of small liquid quantities on a reaction surface: use a paper towel to wipe up the liquid, rinse with a small portion of DI water, and dispose in solid waste

Names and Formulas:

Given a small scale pipette labeled with a chemical formula of an aqueous ionic compound, be able to write the NAME according to rules of nomenclature
Given a small scale pipette labeled with the name of an aqueous ionic compound, be able to write the corresponding FORMULA

Conversions with moles & Avogadro's Number
Lewis Dot Structures & VSEPR Theory
Error Analysis for all experiments
Solubility Rules & Reactions of Aqueous Ionic Compounds:

Given two aqueous ionic compounds, properly mix the solutions, collect observations and write the balanced equation for any reaction observed:

Is a precipitate generated? What is the likely identity of the precipitate? Use the solubility guidelines to decide:

Compounds of hydroxide, phosphate and carbonate are almost always INSOLUBLE
Compounds of sodium, potassium, ammonium, and nitrate are almost always SOLUBLE

Are bubbles produced? What is the likely identity of this gas?

Remember that carbonates (CO₃^2-) react with acids (substances capable of donating H⁺ ions) to produce carbonic acid (H₂CO₃). The carbonic acid then decomposes to produce water and carbon dioxide gas. This is a useful reaction for identifying carbonates.

Use double replacement reactions to identify an unknown ionic compound from a list of possibilities. For example:

How might you test to distinguish between NaCl, Na₂CO₃, & NaNO₃?
How might you test to distinguish between FeCl₃, Na₂SO₄, & HCl?
How might you test to distinguish between NaOH, AgNO₃, & H₂SO₄?

Molar Mass of an Unknown Gas
Acid-Base Titrations:

Know how to properly read and record volumes from a buret. Remember to always estimate between the marks; the burets we use in lab have markings every 0.1 mL, so the volume can be estimated between the marks to the closest 0.01 mL.
Understand how specific errors in the titration could affect the final determination of the acetic acid concentration in vinegar. For example:

Would the final concentration of acetic acid be overestimated, underestimated or remain unaffected, if some of the 10.0 mL of vinegar solution spilled out of the Erlenmeyer flask before the start of the titration?
Would the final concentration of acetic acid be overestimated, underestimated or remain unaffected, if the buret was dirty and the titrant did not fully drain from the sides on the buret (leaving droplets adhered to the glass)?