Chem 1A Lab Final
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.
Which of these bonds is formed due to the opposite charges of cations and anions being attracted to each other?
Ionic
According to solubility rules, which compound should dissolve in water? AgBr MgCO3 K3PO4 CaSO4
K3PO4
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?
Move the beaker to the center of the hot plate. Turn down the stirring speed.
Which of the following salts do you expect to be soluble or sparingly soluble in aqueous solution? Ag2CO3 NaCO3 BaSO4 Fe(OH)2
NaCO3
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.
Are shorts allowed in the lab?
No, only long pants are allowed.
What do you do if a strong acid is spilled on a counter or in the fume hood?
Notify the TA. Use sodium bicarbonate to neutralize the acid and notify the TA.
Suppose a solution contains calcium, Ca2+, ions. According to solubility rules, which other ion should be added to form a precipitate? NO3− Pb2+ Cl− PO43−
PO43-
Suppose a solution contains chloride, Cl−, ions. According to solubility rules, which other ion should be added to form a precipitate? Na+ Pb2+ Ca2+ CO32−
Pb2+
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
Identify which balance was used to make each mass reading. 1.230 g 4.0000 g 6.539 g 5.43 g 0.90 g
-a balance with +-0.001 g tolerance - a balance with +-0.0001 g tolerance -a balance with +-0.001 g tolerance -a balance with +-0.01 g tolerance -a balance with +-0.01 g tolerance
How many liters is 67.7 mL?
.0677 L
How many liters is 85.3 mL?
.0853
Sugar is easily soluble in water and has a molar mass of 342.30 g/mol. What is the molar concentration of a 229.2 mL aqueous solution prepared with 78.5 g of sugar?
.2292 L
If, at 25°C and standard pressure, 3.64 mL of dry air are injected into a graduated cylinder, how many moles of dry air are in the sample space?
0.000149
Sugar is easily soluble in water and has a molar mass of 342.30 g/mol. What is the molar concentration of a 274.6 mL aqueous solution prepared with 73.9 g of sugar?
0.786 M 73.9 g / (342.30 g/mol) = 0.2159 0.2159 / 0.2746 L = 0.786 M
When using the Ideal Gas Law, pressure should be expressed in units of atmospheres. Convert 745.1 mmHg to atmospheres.
0.9804 atm
To convert between units, you need to know the relationship between units. For example, one mile equals 5280 feet. This relationship can now be used as a conversion factor, set up as required by the question. For each conversion, choose the correct arrangement of the conversion factor and complete the calculation. 1. Convert 7860 feet to miles 7860 feet×( A )( B ) 2. Convert 0.565 miles to feet 0.565 miles×( C )( D )
1 mile 5280 feet 1.49 5280 feet 1 mile 2980
Rank the following glassware used in lab from least accurate (1) to most accurate (3). Beaker Graduated cylinder Volumetric pipette
1,2,3
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
What would be the reported length, with correct number of significant figures, of the block shown? (0.5 ruler with 4 tic marks in between, measurement is on 1.0 and 3 and a bit tick marks)
1.38 cm
Select the coefficients necessary to balance each equation. Choose a coefficient for every compound. __CaSO4+ __KOH⟶ __Ca(OH)2+ __K2SO4 __CaCl2 + __Na3PO4⟶ __ Ca3(PO4)2+ __NaCl
1:2:1:1 3:2:1:6
If a photon has a wavelength of 693.7 nm, what is the energy of the photon (in J)?
2.864e-19
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 773.1 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?
24.4 L/mol
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 boat4.327 gMass of weigh boat and sample 7.923 g What is the mass of the solid sample (in g)?
3.605 g
Read the buret, which is marked in mL, in the pictured close-up. Make sure to report your reading with the appropriate significant figures. (goes by 1 ml with 10 tick marks in between, level is at 40 beneath first tick mark)
39.94 mL
Convert 0.45 cm to mm.
4.5 mm
Identify the number of valence electrons in each atom. N B Cl Li Xe Ca
5 3 7 1 8 2
If an electron transition involves 3.47×10−19 J3.47×10−19 J of energy, what is the wavelength (in nm) of the photon that is emitted?
573 nm
Suppose that you decompose 21.92 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 9.21 g of solid NiNi , which has a molar mass of 58.963 g/mol. What is the percent yield of your decomposition? Type answer:
58.925%
Identify correctly formatted scientific notation.
8 x 10^6 6.1 x 10^12 4.532 x 10^-9
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
What occurs when aqueous silver nitrate, AgNO3AgNO3, reacts with aqueous potassium sulfate, K2SO4K2SO4?
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. As gas pressure decreases, its volume increases. 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
To activate the eyewash, push the ________________ towards the wall.
lever
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
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
To handle a hot glass beaker it is best to use, ______ If you burn yourself, immedietely rinse 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, a 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
What is the purpose of stirring a solution while it is being heated?
To help evenly distribute heat throughout the solution.
What should be done if a chemical gets in one of your eyes?
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 you.
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 ____.
an acid and a base, of water and a salt
Name each ionic compound based on its formula. Ca(OH)2 Co3PO4 Al(IO3)3 Na2CO3
calcium hydroxide cobalt(I) phosphate aluminum iodate sodium carbonate
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
Ca2+(aq)+SO42−(aq)⟶CaSO4(s)Ca2+(aq)+SO42−(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)2Na+(aq)+2Br−(aq)+CaSO4(s) _______ CaBr2(aq)+Na2SO4(aq)⟶2NaBr(aq)+CaSO4(s)CaBr2(aq)+Na2SO4(aq)⟶2NaBr(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 _____ How will you dispose of non-toxic waste?______
fume hood, label, trash
To activate the safety shower, pull down on the ______________________.
handle
What precautions should you take if you boil or heat a solution?
You should never leave the solution unattended. As long as you watch the solution closely, you can work on other parts of the experiment. When boiling a solution, you should use boiling chips to prevent splattering. You should always wear eye protection and secure long hair. You should make sure the beaker or flask rests securely on the ring stand or hot plate.
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.
What is the name of the compound with the formula of BF3?
Boron Trifluoride
Identify tools that are ideal for cleaning glassware.
Brushes Detergent and water
What visible sign does NOT indicate a precipitation reaction when two solutions are mixed?
Bubbling in the test tube.
What is the correct net ionic equation to describe this precipitation reaction? Co(NO3)2(aq)+2NaOH(aq)⟶2NaNO3(aq)+Co(OH)2(s)
Co2+(aq)+2OH−(aq)⟶Co(OH)2(s)
Phosphate, (PO4)3- , is a polyatomic ion that can combine with any cation to form an ionic compound. Identify all the formulas below that correctly represent phosphate compounds.
Combined with lithium: Li3PO4 Combined with magnesium: Mg3(PO4)2 Combined with iron(III): FePO4 Combined with copper(I): Cu3PO4
Where should glassware be stored after it is cleaned?
In a drying oven, or designated locations such as drawers or buret racks.
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 visible sign does indicate a precipitation reaction when two solutions are mixed?
Solid settling to the bottom. Solution becoming cloudy. Particulate solid matter floating.
Match each formula to its name. SF4 S2F10 PBr3 PBr5 ClO2
Sulfur tetrafluoride Disulfur decafluoride Phosphorus tribromide Phosphorus pentabromide Chlorine dioxide
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
Identify the correct name for each acid. HClO3 HNO2 H2SO4 H2S HNO3 HClO4
chloric acid nitrous acid sulfuric acid hydrosulfuric acid nitric acid perchloric acid
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. Blue line: Violet line: Red line:
n=5 to n=2 n=6 to n=2 n=3 to n=2
To isolate a single variable when rearranging equations, move all other variables to the _____ of the equation by using _____ on them and remembering to perform that operation _______. Make sure the rearrangement has the target variable _______.
other side, the opposite function, on both sides of the equation, in the numerator not the denominator
Dalton's Law of Partial Pressures states that the total pressure of a gas mixture is equal to the sum of the _____ as long as the gases _____.
partial pressures of all the component gases, do not react with each other
A _____ study is characterized by precise measurements and numerical data, while a _____ study is characterized by a lack of precise numerical data.
quantitative, qualitative
A thermometer is placed such that the bulb makes poor contact with the measured substance, giving erratic temperature readings. 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. The last digit on a pH meter fluctuates up and down as a measurement is taken.
random, systematic, random
Arrange the colors of the visible spectrum in order from highest to lowest energy.
violet - Highest energy blue green yellow orange red - Lowest energy