Chemistry Lab Questions

When electricity passes through a gas element in a discharge tube, light is given off. What is the cause of this phenomenon?

Electricity excites electrons from the element into higher energy states. The electrons then return to the ground state, releasing energy corresponding to the wavelengths of the light seen.

If the ratio of the moles of Cl to Fe in a compound was found to be 2.981, what would be the empirical formula of the compound?

FeCl3

Which procedure cannot be performed on a hot plate, requiring a Bunsen burner instead?

Heating a crucible to remove water from a hydrate

Arrange the colors of the visible spectrum in order from highest to lowest energy.

Highest energy, violet, blue, green, yellow, orange, red, lowest energy

According to solubility rules, which compound should dissolve in water?

K3PO4 STUDY MORE

Which of the following salts do you expect to be soluble or sparingly soluble in aqueous solution?

NaCO3 STUDY MORE

What needs to be included in the label for each axis of a graph?

Name of quantity displayed on axis, Units of quantity displayed on axis

Suppose a solution contains calcium, Ca2+Ca2+, ions. According to solubility rules, which other ion should be added to form a precipitate? Select one:

PO43-

How do you dispose of broken glassware, such as a broken test tube or beaker that contains a chemical residue?

Place in the red can labeled "glass only"

In the Ideal Gas Law, what does P stand for?

Pressure

Which is an example of an accurate manipulation of the Ideal Gas Law?

(PV)/R=nT

How many kilometers is 3444.2 cm?

0.034442

How many liters is 89.2 mL?

0.0892

When using the Ideal Gas Law, pressure should be expressed in units of atmospheres. Convert 745.1 mmHg to atmospheres. Select one:

0.9804 atm

Sugar is easily soluble in water and has a molar mass of 342.30 g/mol. What is the molar concentration of a 228.6 mL aqueous solution prepared with 77.8 g of sugar?

0.994

Rank the following glassware used in lab from least accurate (1) to most accurate (3).

1 Beaker, 2 Graduated Cylinder, 3 Volumetric Pipette

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? Use correct significant figures when answering this question

1.3

If, at 25°C and standard pressure, 3.85 mL of dry air are injected into a graduated cylinder, how many moles of dry air are in the sample space?

1.57x10^-4

Knowing that one day is 24 hours, how many days is 50.9 hours?

2.12 days

Suppose you are measuring the mass of a solid sample on a balance using a weigh boat. You record the data in a table. Mass of weigh boat2.336 gMass of weigh boat and sample 5.024 g What is the mass of the solid sample (in g)? Type answer:

2.688

Suppose you are performing a gas-producing reaction to experimentally determine the molar volume of the gas. A sample of produces 21.5 mL ofgas. The gas is collected over water at an atmospheric pressure of 765.1 mm Hg at 22 oC, at which the vapor pressure of water is 19.8 mm Hg. What is the experimental value for the molar volume of the hydrogen gas in L/mol?

24.66

How many significant figures are in the number 0.0000409? Give a numerical answer.

3

If a photon has a wavelength of 547.5 nm, what is the energy of the photon (in J)?

3.63x10^-19

Read the buret, which is marked in mL, in the pictured close-up. Make sure to report your reading with the appropriate significant figures.

39.95 PRACTICE MORE

Identify correctly formatted scientific notation. Select one or more: 4.532×10−9 9.31×100−7 6÷10^6 0.802×104 6.1×1012 8×106

4.532×10−9, 6.1×1012, 8×106

Convert 0.45 cm to mm.

4.5mm

Identify which balance was used to make each mass reading.

5.43, 1.230, 6.539.....

Suppose that you decompose 28.84 g of Ni2O3Ni2O3 , which has a molar mass of 165.39 g/mol, into nickel and oxygen. 2Ni2O3(s)⟶4Ni(s)+3O2(g)2Ni2O3(s)⟶4Ni(s)+3O2(g) After completing the decomposition, you have 10.59 g of solid NiNi , which has a molar mass of 58.963 g/mol. What is the percent yield of your decomposition? Type answer:

51.5% DO PROBLEM

What is the literature value of the gas constant, R, in units of L⋅kPamol⋅KL⋅kPamol⋅K ? Report the value with at least three significant figures.

8.314

If an electron transition involves 2.47×10−19 J2.47×10−19 J of energy, what is the wavelength (in nm) of the photon that is emitted?

805

What occurs when aqueous silver nitrate, AgNO3AgNO3, reacts with aqueous potassium sulfate,2SO4K2SO4?

Ag2SO4Ag2SO4 forms as a precipitate

What is the correct formula for aluminum hypochlorite?

Al(ClO)3

According to Boyle's Law, what should happen to the pressure of an ideal gas when its volume is increased at the same temperature?

The pressure of the gas decreases

Which observations support Boyle's Law?

The product of a gas's pressure and volume is constant, When volume of a gas is decreased, its pressure will increase

Look up the word titrant. What is a titrant?

The solution dispensed from the buret during a titration

What is the analyte in an acid-base titration experiment?

The solution of an unknown concentration that has another solution slowly added to it

Which of these bonds is formed due to the opposite charges of cations and anions being attracted to each other?

ionic

A study is characterized by precise measurements and numerical data, while a study is characterized by a lack of precise numerical data.

quantative, qualatative

If a large amount of a caustic chemical spills on your clothes, or if your clothing catches on fire, you need to use the:

safety shower

Determine where each type of cleaning solution should be discarded after use. Water used to rinse detergent out of a flask The solvent used to rinse chemicals out of a beaker Acid solution used to clean a crucible

sink, waste container, waste container

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

slit, diffraction grating, wavelength scale

Select the coefficients necessary to balance each equation. Choose a coefficient for every compound.

stochiometry

Dalton's Law of Partial Pressures states that the total pressure of a gas mixture is equal to the of the as long as

sum, partial pressures of all the component gases, the gases do not react with each other

Identify the following errors as systematic or random. 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. A thermometer is placed such that the bulb makes poor contact with the measured substance, giving erratic temperature readings. The last digit on a pH meter fluctuates up and down as a measurement is taken.

systematic, random, random

What should you do every time you are about to heat glassware on a hot plate?

that there are no cracks in the glassware Inspect the hot plate for frayed cords Ensure that the glassware is designed for heating

To handle a hot glass beaker, it is best to use: If you burn yourself, immediately rinse the area with Acids and bases, such as NaOH and HCl, are strong and can cause burns. In case of contact with your skin, rinse immediately with

tongs, water, water

When an electron moves up to higher energy levels, the atom a photon of light whereas the atom a photon of light when an electron drops to a lower energy level. The photons emitted from an atom appear as

absorbs, emits, line spectrum

The lid on a waste jar should never be tight, and a waste jar should not be filled past the bottom of the neck. Why not?

To ensure that the waste can be easily accessed, and that there is ample room for the waste and its vapors

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?

Turn down the stirring speed, Move the beaker to the center of the hot plate

What should be done if a chemical gets in one of your eyes? Select any applicable answer.

Use the eyewash station, being careful not to rub your eye, Use a flexible hose on a faucet to rinse your eye, being careful not to rub your eye.

Determine when you should remove your goggles in the lab room.

When everyone in the room is done handling any chemicals or glassware

A neutralization reaction is a reaction between that results in the formation of and

an acid and a base, water, and a salt

When cleaning a buret, begin by coating the inside with Empty most of it out, then drain the rest by Rinse with then hang upside-down on a buret rack.

detergent solution, opening the stopcock, deionized water

Determine the type of each chemical equation describing a precipitation reaction. CaBr2(aq)+Na2SO4(aq)⟶2NaBr(aq)+CaSO4(s)CaBr2(aq)+Na2SO4(aq)⟶2NaBr(aq)+CaSO4(s) Ca2+(aq)+2Br−(aq)+2Na+(aq)+SO42−(aq)⟶Ca2+(aq)+2Br−(aq)+2Na+(aq)+SO42−(aq)⟶ 2Na+(aq)+2Br−(aq)+CaSO4(s) Ca2+(aq)+SO42−(aq)⟶CaSO4(s)

full molecular equation, full ionic equation, net ionic equation

All chemical waste in the lab is disposed of in an appropriate waste jar located in the Before you pour chemical waste into a waste jar, you must first read the Choose How will you dispose of non-toxic waste?

fume hood, label, trash

What should you do with chemical waste when the waste jar in the hood is filled to the bottom of the neck?

Ask the stock room personnel to bring another waste jar.

Identify tools that are ideal for cleaning glassware. Select one or more:

Brushes, Detergent and water

What visible sign does NOT indicate a precipitation reaction when two solutions are mixed?

Bubbling in the test tube

What do you do if a strong acid is spilled on a counter or in the fume hood?

C) Notify the TA D) Use sodium bicarbonate to neutralize the acid and notify the TA E) Either C or D

Name each ionic compound based on its formula.

Ca(OH)2Ca(OH)2: Calcium Hydroxide Co3PO4Co3PO4: Cobalt phosphate Al(IO3)3Al(IO3)3: Aluminum iodate Na2CO3Na2CO3: Sodium Carbonate

Match each formula to its name. ClO2

Chlorine Dioxide

What is the correct net ionic equation to describe this precipitation reaction? Co(NO3)2(aq)+2NaOH(aq)⟶2NaNO3(aq)+Co(OH)2(s)Co(NO3)2(aq)+2NaOH(aq)⟶2NaNO3(aq)+Co(OH)2(s)

Co2+(aq)+2OH−(aq)⟶Co(OH)2(s)

What precautions should you take with long hair?

Long hair must be secured with a rubber band, barette, or headband

Suppose you measure out 2.45 g of a metal, which corresponds to 0.0908 mol of the metal, and react with enough hydrochloric acid to produce 12.11 g of the metal chloride. Based on the data, what is the formula for the chloride you produced?

MCl3

What practice will not help you make an accurate volume reading on a buret at the beginning of a titration?

Make sure that the meniscus starts exactly at 0.00 mL

What is the name of the compound with the formula of BF3 ?

boron trifluoride

In order to use a pipet, place a at the top of the pipet. Use this object to fill the pipet such that the of the liquid is even with the volume line. Release the liquid, touching the tip of the pipet to the side of the container if necessary to release the last drop the pipet tip

bulb or pump, meniscus, outside

Determine the relative order of the metric prefixes of kilo-, micro-, centi-, and milli-. For the same base unit, is less than , which is less than, which is less than

micro, milli, centi, kilo

Consider the diagram of the energy levels in a hydrogen atom, determine the most likely electron transition corresponding to each color on a line spectrum. Each transition will be used once.

red line n=3 to n=2, violet line n=6 to n=2, blue line n=5 to n=2

Identify the number of valence electrons in each atom.

you know it