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Gen Chem (1)
| Question | Answer |
|---|---|
| What is a beaker used for? | Heating, mixing, or stirring solutions. Wide-mouth with a spout. NOT accurate for measuring volumes. |
| What is a graduated cylinder used for? | Measuring liquid volumes. Narrower and taller than beakers. More accurate than beakers, but pipettes/burettes/volumetric flasks are better for high accuracy. |
| What are test tubes used for? | Holding small volumes, mixing, comparing samples by color. Can be heated, cooled, or stored. NOT used to measure volumes. |
| What is an Erlenmeyer flask used for? | Mixing, heating, stirring, and swirling solutions. Preferred over beakers for swirling (less spill risk). Also used in titrations. NOT accurate for volume measurement. |
| What is a volumetric flask used for? | Obtaining a very specific volume of liquid (single marking on neck). Used for preparing or diluting solutions. Capped to prevent evaporation. |
| What is a boiling flask (round-bottom flask) used for? | Swirling and heating liquids. Requires a clamp or corkscrew ring to stand. NOT used to measure volumes. |
| What are droppers (Pasteur pipettes) used for? | Delivering liquid (usually an indicator) in a drop-wise fashion. Small glass tube with a rubber bulb. |
| What are pipettes used for? | The most precise glassware for measuring and transferring a specific volume of liquid. Can be graduated, volumetric, or electronic. |
| What is a burette used for? | Dispensing highly precise volumes of liquid. Used in titrations to deliver a titrant. Has a stopcock to control flow. Long, graduated glass tube. |
| What is a Bunsen burner used for? | Producing an open flame for heating. Connected to natural gas via rubber tubing. Has a valve (gas flow) and collar (airflow). Lit with a striker. |
| What is a pH meter used for? | Accurately measuring the pH of a solution. Must be calibrated before each use. |
| What is a digital balance used for? | Accurately measuring the mass of a solid sample. The "tare" button resets the reading to zero to exclude the weight of the container. |
| What is a meniscus and how do you read it? | The curved surface of a liquid in glassware — higher at the edges, lower at the center. Always read from the bottom of the meniscus with eyes level to the glassware. |
| How do you calculate volume in a reverse-numbered burette? | Volume = V(total) − V(reading). Example: if the burette reads 11 mL and total volume is 50 mL, then volume = 50 − 11 = 39 mL. |
| What is the order of precision for volume measurement (most to least)? | Pipettes > Burettes/Volumetric Flasks > Graduated Cylinders > Beakers/Erlenmeyer Flasks. |
| What does "volumetric" glassware mean vs. "graduated"? | Volumetric = single marking for one specific volume (more precise). Graduated = multiple markings for different volumes (less precise). |
| How do you properly measure the mass of a solid sample? | Place weighing paper or glassware on the balance first, press tare to zero it out, then add the sample. Never place the sample directly on the balance. |
| What is centrifugation? | A process using a centrifuge to separate mixture components by spinning at high speeds. Denser solids form a pellet at the bottom; liquid supernatant sits on top. |
| How do you separate a solid pellet from liquid supernatant after centrifugation? | Use a pipette to remove the liquid, or decant (pour off) the liquid, leaving the solid behind. Filtration can also be used. |
| What is titration? | A method of delivering a titrant drop-by-drop via a burette to a solution to determine the unknown concentration. The equivalence point is when the titrant has completely reacted with the reagent. |
| What is the difference between equivalence point and endpoint in titration? | Equivalence point = titrant has completely reacted with the reagent. Endpoint = observable change (e.g., color change). Any deviation between them is titration error. |
| What is calorimetry? | A method to measure heat energy released or absorbed during a chemical reaction. Basic setup uses a Styrofoam cup, lid, and thermometer. Determines if a reaction is exothermic (releases heat) or endothermic (absorbs heat). |
| What is a safety shower used for? | Delivers a continuous stream of water for anyone splashed with toxic/corrosive chemicals or whose clothing has caught fire. |
| What is an eye wash station used for? | Treats chemical splashes in or near the eyes. Rinse thoroughly with both eyes open. |
| What is a fume hood used for? | Provides ventilation to minimize exposure to harmful vapors. Volatile substance containers should be covered with a watch glass when not in use. |
| When should fire extinguishers be used and how? | For solvent or electrical fires only (NOT paper or wood). Aim at the base of the fire closest to you. Position yourself between the fire and the exit. |
| What personal protective equipment (PPE) is required in the lab? | Lab coat, safety goggles, gloves, and closed-toed shoes. Avoid contact lenses even with goggles — fumes can concentrate underneath. |
| How should broken glass be handled? | Clean up immediately and carefully using a dustpan. Dispose of in the designated broken glass container. |
| How do you properly dispose of chemical solutions? | Acids, alkalis, and water-miscible solutions can be poured down the drain with water. Organic and water-immiscible chemicals go in the appropriate waste bin — NOT down the drain. |
| What are three things you should NEVER do in the lab? | Never eat or drink in the lab, never add water directly to concentrated acid (add acid to water instead), and never pipette by mouth. |
| What is accuracy vs. precision? | Accuracy = how close a measurement is to the true/literature value. Precision = how consistent repeated measurements are with each other. A value can be precise but inaccurate, or accurate but imprecise. |
| What are the four rules for significant digits? | 1) All non-zero digits are significant. 2) Zeros between two non-zero digits are significant. 3) Trailing zeros after a decimal point are significant. 4) All other zeros are NOT significant (e.g., 500 or 0.003). |
| How do you handle significant digits in multiplication/division? | Round the answer to the same number of sig figs as the measurement with the fewest sig figs. |
| How do you handle significant digits in addition/subtraction? | Round the answer to the least precise decimal place among all measurements. |
| What is systematic error? | Error consistently skewed in one direction by the same amount each time. Caused by faulty equipment or procedural errors (e.g., forgetting to tare the balance). |
| What is random error? | Error that varies in direction and magnitude each time. Caused by human error (e.g., inconsistent meniscus readings, reaction time with a stopwatch). |
| What is the formula for percent error? | % error = (|experimental − actual| / actual) × 100% |
| What is decanting? | A separation technique where the liquid (supernatant) is simply poured out of a vessel, leaving the solid behind. Commonly used after centrifugation to separate the liquid supernatant from the solid pellet. |
Created by:
smurtab