CHM 161 Labs 4-6 Review

Burning 1.06 g of a fuel causes the water in a calorimeter to increase by 11.2∘C. If the calorimeter has a heat capacity of 3.09 kJ/∘C, what is the energy density of the fuel (in kJ/g)?

-32.6 kJ/g

Consider the combustion of heptane, C7H16, according to the balanced equation C7H16+11O2⟶7CO2+8H2O+ Using the given enthalpies of formation, ΔH∘f for each species, determine the enthalpy of combustion of heptane. C7H16=−224 O2=0 CO2=−394 H2O=−242

-4470 kJ/mol

If a photon has a wavelength of 664.8 nm, what is the energy of the photon (in J)?

2.988*10^-19 J

Suppose you are working with a NaOH stock solution but you need a solution with a lower concentration for your experiment. Calculate the volume (in mL) of the 1.351 M stock NaOH solution needed to prepare 250.0 mL of 0.1244 M to dilute NaOH solution.

23.02 mL

Suppose you need to calibrate a calorimeter. You burn 0.928 g of a fuel with an enthalpy of combustion of −48.7 kJ/g If the temperature of water in the calorimeter increases by 12.9∘C during the reaction, what is the heat capacity of the calorimeter?

3.50 kJ/C

If an electron transition involves 4.84×10−19 J of energy, what is the wavelength (in nm) of the photon that is emitted?

410 nm

Identify the molecules that are produced in the combustion of every hydrocarbon fuel. Select one or more: A: Hydrogen B: Carbon dioxide C: Water D: Oxygen

B: Carbon dioxide C: Water

Identify the pieces of glassware that are most effective for accurate solution preparation. Select one or more: A: Erlenmeyer flask B: Volumetric pipette C: Graduated cylinder D: Volumetric flask

B: Volumetric pipette D: Volumetric flask

Write the net ionic equation for this molecular equation Co(NO3)2(aq)+2NaOH(aq)⟶2NaNO3(aq)+Co(OH)2(s)

Co2+(aq)+2OH−(aq)⟶Co(OH)2(s)

Which of the following compounds requires a Roman numeral in its name? Select one: A: MgCl2 B: Al(NO3)3 C: Na2O D: MnO2

D: MnO2

Fuel A has an energy density of −46.3 kJ/g and Fuel B has an energy density of −35.4 kJ/g The fuel with greater energy density is Fuel B/Fuel A because you need to burn more/less of Fuel A than Fuel B to produce the same amount of heat.

Fuel A, less

Identify the equipment best suited for extinguishing each type of fire. large fire on floor small bench top fire clothing fire

fire extinguisher, overturned beaker, fire blanket

A calorimeter measures the heat/moles/mass involved in reactions or other processes by measuring the enthalpy change/temperature change/mass gain of the materials surrounding/produced by/involved in the process. The calorimeter is insulated/conductive/left open to prevent the transfer of heat to outside the device.

heat, temperature change, surrounding, insulated

To prepare a standard (calibration) curve for a spectroscopy experiment, start by preparing one solution/multiple solutions with different known concentrations/different unknown concentrations/an unknown concentration. Then, measure the absorbance/wavelength/concentration of each solution at the same concentration/different wavelengths/the same wavelength and create a plot of absorbance vs. wavelength/absorbance vs. concentration/wavelength vs. concentration for the measured values. Finally, find the best-fit line of the data set.

multiple solutions, different known concentrations, absorbance, the same wavelength, absorbance vs. wavelength

To use a spectroscope, position the tool to allow light to enter through the wavelength scale/slit/diffraction grating. The light will reflect off the slit/wavelength scale/diffraction grating, which separates it into colors. View the results on the slit/diffraction grating/wavelength scale.

slit, diffraction grating, wavelength scale

When testing the pH of a solution with litmus paper, dip a stirring rod/the paper in the solution. Add a drop/thin coating of the solution to the paper. Observe the color/size of the litmus paper and determine whether the solution is acidic or basic.

stirring rod, drop, color

Glucose (molar mass=180.16 g/mol) is a simple, soluble sugar. Glucose solutions are used to treat patients with low blood sugar. Suppose you prepare a glucose solution using the described procedure. Step 1: Dissolve 294.9 g of glucose in enough water to make 500.0 mL of solution. Step 2: Transfer 20.2 mL of the solution to a new flask and add enough water to make 250.0 mL of dilute solution. What is the molar concentration of the glucose solution at the end of the procedure?

0.264 M

How can you improve your ability to see changes corresponding to reactions in a spot plate? Select one: A: Compare the spot plate on light and dark backgrounds, such as white paper and the bench. B: Hold the spot plate over your head and look at it from underneath towards the light. C: Add acid to any questionable results to force the changes to appear. D: Keep adding both reagents to the well until you are sure you see a change.

A: Compare the spot plate on light and dark backgrounds, such as white paper and the bench.

Determine which of the following processes are endothermic A: Ice melts into liquid water B: Solid dissolves into solution, making ice pack feel cold C: A process with a calculated positive q D: A process with a calculated negative q E: Wood burns in a fireplace F: Acid and base are mixed, making test tube feel hot

A: Ice melts into liquid water B: Solid dissolves into solution, making ice pack feel cold C: A process with a calculated positive q

If you spill fuel while working with the fuel burners, what should you do? Select one or more: A: Make sure there are no open flames or sources of ignition around when cleaning. B: Wipe it up before telling anyone about the spill to address it quickly. C: Clean up the spill by igniting the spilled fuel and burning it off the surface. D: Inform the instructor and everyone working around the area about the spill.

A: Make sure there are no open flames or sources of ignition around when cleaning. D: Inform the instructor and everyone working around the area about the spill.

Identify the true statements describing the use of the fuel burners in the Thermochemistry experiment. Select one or more: A: The burner should be lit for 20 seconds after any change before proceeding. B: The burner wick should be about a few millimeters above the metal stem. C: The cap should be left on the fuel burner whenever it is not in use. D: The burner should be turned upside down to lengthen the wick, if needed.

A: The burner should be lit for 20 seconds after any change before proceeding. B: The burner wick should be about a few millimeters above the metal stem. C: The cap should be left on the fuel burner whenever it is not in use.

What is the best safety approach when working with unknown chemical substances? Select one: A: Do not begin working with a substance unless you know exactly what it is. B: Assume that the substance is hazardous. Always wear appropriate PPE and take steps to prevent contact. C: Assume that any substance distributed to lab participants is non-toxic and not a safety risk. D: Read the procedure and try to guess what the unknown substance is, then review its specific safety information.

B: Assume that the substance is hazardous. Always wear appropriate PPE and take steps to prevent contact.

When you mix a bicarbonate or carbonate compound and acid, why are bubbles formed? Select one: A: The acid solution is boiling off. B: Carbon dioxide gas is being formed. C: Acid gas is being formed. D: Sodium bicarbonate is subliming off.

B: Carbon dioxide gas is being formed.

Identify the common indicators that a chemical reaction has occurred. Select one or more: A: A solid being dissolved B: Precipitate being formed C: Bubbles being produced D: A phase change E: A change in temperature F: A color change

B: Precipitate being formed C: Bubbles being produced E: A change in temperature F: A color change

What is the general definition of heat capacity? Select one: A: The energy that exchanges with the surroundings due to a difference in temperature B: The change in heat required to change the temperature of something by one degree Celsius C: The determination of whether heat is consumed or given off from one gram of a substance D: The ability of a reaction to consume or give off heat based on the mass of its reactants

B: The change in heat required to change the temperature of something by one degree Celsius

What visible signs indicate a precipitation reaction when two solutions are mixed? Select one or more: A: Bubbling in the test tube B: A color change C: A hazy or cloudy appearance D: Solid settling out in the test tube

C: A hazy or cloudy appearance D: Solid settling out in the test tube

What is the goal of qualitative analysis? Select one: A: Removing components from a substance B: Calculating the mass or concentration of each component in a substance C: Determining the composition of a substance D: Assessing the quality of a substance

C: Determining the composition of a substance

Which compound name does not correspond to an ionic compound? Select one: A: Silver iodide B: Molybdenum(V) chloride C: Phosphorus pentafluoride D: Magnesium bromide

C: Phosphorus pentafluoride

Identify the main reason for adding the solvent slowly to a volumetric flask. Select one: A: To ensure that the solvent has time to thoroughly dissolve any solute B: To allow the air in the flask to become saturated with solvent C: Because volumetric flasks are fragile and can break if a liquid is added too fast D: So that the liquid does not exceed the volume marking on the flask

D: So that the liquid does not exceed the volume marking on the flask

When preparing a dilute solution from a more concentrated one, be sure to carry out the necessary calculations before/while/after getting started with any glassware. Use a volumetric pipette/graduated pipette/graduated cylinder to transfer an aliquot of the concentrated solution into a clean, dry volumetric flask. Add a small amount of solvent, swirl the flask, then fill to the volume marking/top/halfway point Mix the solution and label the flask.

before, volumetric pipette, volume marking

Determine which concentration unit is best for each scenario. You want to study the reaction between two solutes when mixing their solutions. You want to measure a very small, trace element in water. You want to study the impact of the solute on the solvent's properties.

molarity, parts per million, molality

When electrons in an element drop to lower energy levels, photons/kilojoules/molecules of energy are emitted. The energy of the emitted light can be seen on a line spectrum/continuous spectrum/infrared spectrum. The set of colors corresponding to the electron transitions within each element are the same/invisible/unique for each element.

photons, line spectrum, unique

In the Chemical Clue lab, the dropper bottles containing the Known anions are all phosphate/sodium/nitrate/iron salt solutions. The dropper bottles containing the Test Reagent cations are all iron/sodium/phosphate/nitrate salt solutions. These salts ensure that all the reagent compounds melt into liquid/create bubbles/dissolve in the water/form a precipitate in the dropper bottles.

sodium, nitrate, dissolve in water