CH 202 Final

When operating the centrifuge, students should do which of the following?

-Centrifuge for approximately 30 seconds. -Make sure that the lid is completely shut and the safety knob is turned to engage the safety switch

What are the standard ways to make a solution of known concentration?

-Dilute a known volume of stock solution into a known volume of liquid. -Dissolve a weighed amount (known mass) of solid into a known volume of liquid.

What should be done to waste solutions containing copper ion?

-It should be dumped in a beaker labeled "waste copper" on one's bench during the experiment. -It should be disposed of in the bottle for waste copper ion when work is completed.

Which of the following are hazardous properties of nitric acid?

-It's an oxidant -It's corrosive

Which of the following are hazardous properties of copper nitrate, Cu(NO3)2

-It's an oxidizer. -It's corrosive.

Which of the following are hazardous properties of sodium thiocyanate?

-It's toxic -It's an irritant

Stearic and lauric acids are ____________ but prolonged contact with skin may cause ____________

-Nonhazardous -Irritation

Which of the following is a colligative property?

-Osmotic pressure -Vapor pressure lowering -Freezing point depression -Boiling point elevation

Which of the following chemicals are listed as hazardous?

-Phosphoric acid -Ammonia

When placing test tubes in the centrifuge, what are the best practices?

-Place test tubes containing approximately equal volumes in opposite positions on the rotor. -Never put stoppers or other items in the centrifuge with your tubes.

What clothing is appropriate for the laboratory?

-Shoes that cover heels and toes -Pants that extend to the ankles -Shirt and pants that overlap 6" -A shirt that covers the shoulders (has sleeves)

What actions should be taken if you spill a corrosive chemical on your skin?

-The first thing I should do is flush the area with water. -I should have my lab partner report the incident to the instructor.

When working with a buret, one should take care that...

-The tube below the stopcock is completely filled -The buret is conditioned by rinsing it with titrant before use. -The last drop of liquid on the tip is flushed into the analyte.

Which hazards are associated with copper(II) sulfate?

-Toxic -Irritant

When the centrifuge process is complete, students should do which of the following?

-Using the eyehole on top, monitor the spinning rate and open the lid only after the rotor has slowed significantly. -Wait for the rotor to come to a complete stop before attempting to remove your test tubes.

Volumes obtained with volumetric flasks, pipettes, and burets are recorded to the nearest ______ mL

0.01

In the Beer's Law equation, A = E l C, what does the A represent with units?

Absorbance, which is unitless

Which of the chemicals is a respiratory hazard with vapors that should not be inhaled?

Ammonia

The formula for predicting freezing point depression is Delta Tf = mckf. What does Delta Tf represent with units?

Amount freezing point is lowered in degrees C

In the Beer's Law equation, A = E l C, what does the l represent with units?

Cell/vial path length, usually in cm

The formula measuring changes in heat is q = ms Delta T. What does Delta T represent with units?

Change in temperature, usually in·°C

According to the Introduction of this experiment, when the reactants are mixed, what is expected to happen to the color?

Changes from colorless to red

The formula for predicting freezing point depression is Delta Tf = mckf. What does mc represent with units?

Colligative molality which is the number of particles the material forms when it dissolves (van't Hoff factor) multiplied by the concentration in mol solute / kg solvent

In the Beer's Law equation, A = E l C, what does the C represent with units?

Concentration, usually in M

Volumetric flasks are built to _________ a known volume of liquid to an accuracy of about 0.1 % of the flask's capacity.

Contain

Most pipettes are built to _________ a known volume of liquid

Deliver

The wastes in the Determination of an Equilibrium Constant Experiment should be what?

Disposed of in the labeled container.

Which terms below are also descriptive of the heat of neutralization to be measured in Part C of this experiment?

Enthalpy of reaction

What actions should you take if you spill copper(II) sulfate solution on yourself?

Flush the affected area with water.

If any of the solutions in this experiment are spilled on skin or clothing, what is the first thing to do?

Flush the area with water.

The formula for predicting freezing point depression is Delta Tf = mckf. What does kf represent with units?

Freezing point depression constant in units of C/m

If any of the solids in this experiment come into contact with your skin or clothing, what is the first thing to do?

Gently brush the solid off with a paper towel.

Give a brief description of the how heat transfer is measured for a system using the surroundings.

In the calorimetry lab, changes for a system (cooling of a hot metal, chemical reaction, dissolution) are measured by the changes in the surroundings (water). In an insulated system, the heat that the system gains or loses should be exactly matched in magnitude, but opposite in sign, from the changes in the surroundings.

In the Beer's Law equation, A = E l C, what does the E represent with units?

Molar absorptivity in units of cm-1M-1

What does n represent in the Ecell formula?

Moles of electrons

When draining the pipet,...

One allows the liquid to flow out with gravity, then touches the pipet tip to receiving vessel to remove the last drop

Which of the chemicals is corrosive?

Phosphoric acid

It is good practice to "condition" a pipet before using it by...

Rinsing it with a few milliliters of the solution that will be pipetted.

When working with a volumetric pipet, one adjusts the liquid level...

So the bottom of the meniscus is at the scribed line on the pipet.

The formula measuring changes in heat is q = ms Delta T. What does s represent with units?

Specific heat, usually in J/g·°C

What is assumption we are trying to validate in Part A of the calorimetry experiment?

Styrofoam cups isolate the system and surroundings from the rest of the universe.

Give a brief description of the Colligative Properties lab experiment

The Colligative Properties lab was designed to determine the effect on the freezing point of stearic acid when small amounts of lauric acid are added. Each addition lowered the freezing point.

The formula measuring changes in heat is q = ms Delta T. What does q represent with units?

The heat of the change, typically in J or kJ

When pouring two liquids together in the Styrofoam cup calorimeters, why should care be taken to avoid splashing or spilling the liquid?

The mass of the liquids are part of the calculations; loss of mass affects accuracy.

The formula measuring changes in heat is q = ms Delta T. What does m represent with units?

The mass of the material, usually in grams

In a Beer's Law plot, what does the slope represent?

The slope is equal to the molar absorptivity x cell path length.

What happens to the temperature change when the amount of non-limiting reactant is doubled?

The temperature change should remain the same.

What happens to the temperature change when the amount of limiting reactant is doubled?

The temperature change will double.

What does Ecell represent?

The voltage at non-standard state conditions in V

What does E noch cell represent?

The voltage at standard state conditions in V

In a Beer's Law plot, what is the x-axis?

The x-axis should be the concentration of what is being measured

In a Beer's Law plot, what is the y-axis?

The y-axis should be the absorbance.

In a Beer's Law plot, what does the y-intercept represent?

The y-intercept is the absorbance of the blank, which in theory should be zero but in real life is usually a small value.

Given the concentrations and volumes of Fe3+ and SCN− to be used in Parts A and B of the experiment, which of the following statements is true?

There is a large excess of Fe3+ for the calibration curve, but roughly equal amounts of the two ions for determining the equilibrium constant.

Which of the following are hazardous properties of potassium iodate, KIO3, and copper iodate, Cu(IO3)2?

They're strong oxidizing agents.

A buret should be conditioned, then filled...

To slightly below the top scribe mark (0.00 mL)

What formula is used to determine the mmol of acid and base in the reaction table?

Volume in mL x concentration in mmol/mL = mmol

If either stearic acid or lauric acid is spilled on the skin, it should be what?

Washed with soap and water

What does Q represent in the Ecell formula?

[products]/[reactants] under non-standard conditions.