CHM 161 Labs 1-3 Review

Perform the calculation, rounding your answer to the proper number of significant figures. 0.8730 ÷ 9.650 =

.09047

How many liters is 91.4 mL?

.0914 liters

Identify the value of the number presented in scientific notation. 7.32×10−4

0.000732

Calculate the moles of ammonia present in a 1.770 g sample if the molar mass of ammonia is 17.030 g/mol.

0.1039 mol

A football field is 120 yards by 53.333 yards. What is the area of the football field in acres if 1 acre=43560 ft2?

1.3 acres squared

Convert 7860 feet to miles

1.49 miles

What is the charge delivered by a current with an average of 0.62 A over 33.0 minutes?

1200 C

Perform the calculation, rounding your answer to the proper number of significant figures. 0.125 + 4.09 + 13.0065 =

17.22

2.01 g, 2.67 g, 2.91 g, 2.37 g, 2.69 g, and 2.87 g What is the average mass of the product based on the six trials?

2.59 g

Knowing that one day is 24 hours, how many days is 63.1 hours?

2.6 days

Consider the balanced reaction of magnesium and oxygen. 2Mg+O2⟶2MgO What mass of MgO can be produced from 1.79 g of Mg and 2.68 g of O2?

2.97 MgO

Consider the balanced equation for the reaction of aluminum with hydrochloric acid. 2Al+6HCl⟶2AlCl3+3H2 Calculate the mass of HCl needed to react with 5.00 g of Al.

20.3 g HCl

What is the molar mass of the hydrate compound with the proposed formula of CrCl3⋅4H2O?

230.44 g/mol

Convert 0.565 miles to feet

2980 feet

Balance the equation: CaCl2 + Na3PO4 ⟶ Ca3(PO4)2 + NaCl

3, 2, 1, 6

What is the molar mass of C2H6?

30.067 g/mol

A cylinder has a diameter of 3.25 cm and a height of 4.65 cm. What is the volume?

38.6 cm^3

How many electrons were transferred if the total charge of a process is 715.2 C?

4.46e21 electrons

Suppose that you decompose 21.92 g of Ni2O3, which has a molar mass of 165.39 g/mol, into nickel and oxygen. 2Ni2O3(s)⟶4Ni(s)+3O2(g) After completing the decomposition, you have 10.08 g of solid NiNi, which has a molar mass of 58.963 g/mol. What is the percent yield of your decomposition?

64.49%

Suppose 3.20 g of copper are reacted with excess nitric acid according to the given equation, and 6.32 g Cu(NO3)2 product are obtained. Cu(s)+4HNO3(aq)⟶Cu(NO3)2(aq)+2NO2(g)+2H2O(l) What is the percent yield of Cu(NO3)2?

66.9 %

When drawing up liquid into a micropipette, put the tip in the liquid at a 45/90 degree angle, push the plunger to the first/second point of resistance, and then hold down/release the plunger. When dispensing that liquid from the micropipette, hold the micropipette at a 45/90 degree angle in the desired container and push the plunger to the first/second point of resistance. Hold down/release the plunger until dispensing is done.

90, first, release, 45, second, Hold down

Identify the true statements concerning Avogadro's number as it applies to atoms or electrons. Multiple answers A: Avogadro's number of electrons is 6.022×10^23 electrons. B: Avogadro's number depends on the charge of the particles. C: The mass of Avogadro's number of atoms depends on the element. D: Avogadro's number is a very small number.

A: Avogadro's number of electrons is 6.022×10^23 electrons. C: The mass of Avogadro's number of atoms depends on the element.

When using a properly stabilized balance, how should you ensure that you get the most accurate mass reading possible? Multiple answers A: Close the side shields on the balance during reading. B: Lean on the table to steady the balance during reading. C: Place the sample on the edge of the balance pan. D: Measure the mass of the sample at room temperature.

A: Close the side shields on the balance during reading. D: Measure the mass of the sample at room temperature.

When inputting a formula into Excel or other spreadsheet software, what components are required for the formula to function properly? Multiple answers A: Closing parentheses for any opening parentheses. B A named function (i.e. SUM) in the formula C: A reference to at least one other cell in the spreadsheet D: An equal sign at the beginning of the formula.

A: Closing parentheses for any opening parentheses. D: An equal sign at the beginning of the formula.

What should you do every time you are about to heat glassware on a hot plate? Multiple answers A: Ensure that the glassware is designed for heating B: Measure the height and width of the glassware C: Check that there are no cracks in the glassware D: Inspect the hot plate for frayed cords

A: Ensure that the glassware is designed for heating C: Check that there are no cracks in the glassware D: Inspect the hot plate for frayed cords

Which procedure cannot be performed on a hot plate, requiring a Bunsen burner instead? One answer A: Heating a crucible to remove water from a hydrate. B: Heating water to boiling for a water bath C: Heating a solvent to help the solute dissolve D: Heating an isolated solid to dry it

A: Heating a crucible to remove water from a hydrate.

Identify effective techniques for accurate pipette use. Multiple answers A: Measure liquid by aligning the meniscus with the volume line. B: Use the pipette bulb to force the last drop out of the tip. C: Leave any air bubbles in a pipette that occur after drawing up liquid. D: Do not let liquid enter the pipette bulb or pump.

A: Measure liquid by aligning the meniscus with the volume line. D: Do not let liquid enter the pipette bulb or pump.

A series of measurements in the lab led to an experimental result of 32.9 mL, with a calculated standard deviation of 0.3 mL. What is the standard way to report this result? One answer A: 32.6 - 33.2 mL B: 32.9 ± 0.3 mL C: ≈ 32.9 mL D: 32.9 ± 0.30 mL

B: 32.9 ± 0.3 mL

Which of the following errors are systematic? Multiple answers A: A thermometer is placed such that the bulb makes poor contact with the measured substance, giving erratic temperature readings. B: A micropipette is improperly calibrated, and the balance dispensed is always smaller than expected. C: A few drops of water are on a balance pan, causing the mass output on the balance to be high each time it is used. D: The last digit on a pH meter fluctuates up and down as a measurement is taken.

B: A micropipette is improperly calibrated, and the balance dispensed is always smaller than expected. C: A few drops of water are on a balance pan, causing the mass output on the balance to be high each time it is used.

What are the best practices while sharing a lab balance with other students? Multiple answers A: Leave a note when you have tared a balance for your glassware. B: Brush off any chemical dust around the balance after each use. C: Alert your TA or instructor about any issues with the balance. D: Place samples directly onto the balance.

B: Brush off any chemical dust around the balance after each use. C: Alert your TA or instructor about any issues with the balance.

A student removes a chemical sample from a reagent bottle to be used in an experiment. What should he do with any excess chemical remaining from this sample after the experiment is complete? One answer A: Discard the chemical down the sink under running water. B: Check and see if anyone else can use the chemical. If not, discard in the proper waste container. C: Clean a spatula thoroughly, then use it to add the chemical back into the reagent bottle. D: Conduct a second trial of the experiment with the excess chemical.

B: Check and see if anyone else can use the chemical. If not, discard in the proper waste container.

How do you determine the last digit in any measured number? One answer A: Consult the unique rule for each type of lab measurement and instrument. B: Estimate one digit past the smallest precisely known digit or marking. C: Record the digit corresponding to the smallest precisely known digit or marking. D: Round up to one digit larger than the smallest precisely known digit or marking.

B: Estimate one digit past the smallest precisely known digit or marking.

What is the purpose of the solvent trap in a vacuum filtration setup? One answer A: Separating the solid component of a mixture from the liquid component B: Keeping the running water from the sink away from the filtration apparatus, and keeping the filtered materials in the filtration apparatus C: Collecting as much of the solvent as possible, so that it can be cleaned and reused in later experiments D: Holding fresh solvent that can be used during the filtration to wash the solid product

B: Keeping the running water from the sink away from the filtration apparatus, and keeping the filtered materials in the filtration apparatus

What statements are always true about limiting reactants? Select one or more: A: The limiting reactant is always the same for a given reaction. B: The limiting reactant is completely used up in the reaction. C: There will be an excess of other reactants at the end of the reaction. D: The limiting reactant has a lower mass than other reactants. E: The limiting reactant dictates the amount of product.

B: The limiting reactant is completely used up in the reaction. C: There will be an excess of other reactants at the end of the reaction. E: The limiting reactant dictates the amount of product.

Identify the true statements describing the experimental set-up in the "Measuring Avogadro's Number" experiment. Multiple answers A: Each set-up should have one strip of copper and one strip of zinc. B: The plastic spacer should be placed between the two strips of metal. C: The metal strip with the red lead is the one that should have its mass measured. D: Only deionized water should be present in the liquid around the metal strips.

B: The plastic spacer should be placed between the two strips of metal. C: The metal strip with the red lead is the one that should have its mass measured.

What is the purpose of stirring a solution while it is being heated? One answer A: To encourage sudden boiling in the solution B: To help evenly distribute heat throughout the solution C: To prevent the solute from dissolving into solution D: To slow down any reactions that occur in the solution

B: To help evenly distribute heat throughout the solution

Which of the following is recommended to keep a pipette clean? Multiple answers A: Turn the micropipette upside down after loading with liquid. B: Use a new tip any time you change solutions. C: Save tips after removal to reuse them later. D: Place the micropipette on the bench between uses. E: Place the micropipette on a rack after using it.

B: Use a new tip any time you change solutions. E: Place the micropipette on a rack after using it.

Identify the recommended practices when putting a tip on a micropipette. Multiple answers A: Hold the micropipette at a 45-degree angle to the tip rack. B: Use the tip size designed for the micropipette size in use. C: Remove the tip from the rack and place it on micropipette by hand. D: Gently push the micropipette into the tip and tap lightly to load the tip.

B: Use the tip size designed for the micropipette size in use. D: Gently push the micropipette into the tip and tap lightly to load the tip.

Which of the following quantities are measured values? Multiple answers A: 3 teacups B: 1 foot = 12 inches C: 2 cups of milk D: 2 avocados E: 144 grams of sugar F: 18 meters

C: 2 cups of milk E: 144 grams of sugar F: 18 meters

What should you do if you are using a balance that has persistent fluctuations in mass? One answer A: Switch to using another balance. B: Record all the fluctuations as your mass reading. C: Contact your TA or instructor to adjust the balance. D: Adjust the feet on the balance yourself.

C: Contact your TA or instructor to adjust the balance.

While setting up a beaker to boil a solution on a hot plate, you notice that the stirring is erratic and unstable. What should you do to stabilize the stirring solution? Multiple answers A: Completely turn off the stirring function. B : Clamp the beaker in place at the edge of the hot plate. C: Move the beaker to the center of the hot plate. D: Turn down the stirring speed.

C: Move the beaker to the center of the hot plate. D: Turn down the stirring speed.

What needs to be included in the label for each axis of a graph? Multiple answers A: Description of how measurement was made B: Relationship to quantity displayed on other axis C: Units of quantity displayed on axis D: Name of quantity displayed on axis

C: Units of quantity displayed on axis D: Name of quantity displayed on axis

When describing the uncertainty of a measurement, the term ____________ refers to the closeness between measurement and its accepted value, whereas the term ____________ refers to the closeness among a set of measurements.

accuracy, precision

Once the vacuum filtration set-up is complete, start by _________________________________ in the filter funnel. Then, ______________ the mixture __________________________________________.

adding a small amount of water, slowly decant, into the middle of the filter paper

The purpose of the best-fit line on an experimental scatter-plot is to identify any linear trend in scattered data/predict behavior between measured data using its slope. The best-fit line allows us to identify any linear trend in scattered data/predict behavior between measured data using its slope.

identify any linear trend in scattered data, predict behavior between measured data using its slope

Systematic error is caused by random fluctuations in a measuring device/improper use of a measuring device, while random error is caused by random fluctuations in a measuring device/improper use of a measuring device.

improper use of a measuring device, random fluctuations in a measuring device

To experimentally determine Avogadro's number, you can apply a current to a metal circuit, causing the metal to lose electrons and dissolve as ions. The number of moles of electrons lost from the metal can be calculated from the total charge and mass change/volume and molar volume/mass change and molar mass of the metal as well as the number of electrons lost/the mass of electrons lost/the total charge of electrons lost in each ion formation. The total number of electrons involved in the process can be calculated from the charge of the metal ions/mass lost by the metal/total charge applied and the individual charge of an electron. Then, Avogadro's number is the molar mass of the metal/number of moles of electrons/total number of electrons divided by the mass of the metal ions/total number of electrons/number of moles of electrons

mass change and molar mass, number of electrons, total charge applied, total number of electrons, number of moles of electrons

In the plot to determine Avogadro's number, the x-axis should be ________________ and the y-axis should be ___________________________. The ______ of the best-fit line should be Avogadro's number

moles of electrons, number of electrons, slope

Suppose you light a Bunsen burner and notice that the flame is very yellow and too short. To get a blue flame, you should open/close the air inlet/gas regulator further. To increase the size of the flame, you should open/close the air inlet/gas regulator further.

open, air inlet, open, gas regulator

Once the separation is complete in a vacuum filtration, stop the process by first opening the clamp or stopper on the solvent trap/turning off the vacuum source and then opening the clamp or stopper on the solvent trap/turning off the vacuum source.

opening the clamp or stopper on the solvent trap, turning off the vacuum source

The comparison of the experimental amount of product to the calculated amount is the __________________. The amount of product experimentally produced is the ________________. The calculated amount of product under ideal conditions is the _______________________.

percent yield, actual yield, theoretical yield

Identify the safety equipment designed to deal with each emergency listed. chemicals on clothes: ______________________ cuts or minor burns: ______________________ chemicals in eyes: ______________________ large fire on the benchtop: ______________________ fire on person: ______________________

safety shower, first aid kit, eyewash station, fire extinguisher, fire blanket