Physical Science Final Exam
Based on your answer to the previous question (Part 2, Question 1), what is the total voltage output for an electrochemical cell made from lead and silver electrodes? lead: -0.13V silver: +0.80V
+0.93V 0.80-(-0.13)= 0.93
Use the bond energies provided on the datasheet of this exam, estimate the energy released or absorbed for the following reaction: 3H2(g) + N2(g) → 2NH3(g)
- 92 kJ/mol
If I dissolve 35.6 grams of aluminum sulfate (Al2(SO4)3) in water to prepare 966 mL solution, the molarity of the Al3+ ions in the resulting aqueous solution will be:
0.215 M
The density of the water in Bangladesh is 0.9970 g/mL. The concentration of arsenic is 1.00 mg per liter of water. Express the arsenic concentration in ppm. The correct answer is:
1.00 ppm
Arsenic poisoning from water contamination is a serious problem in Bangladesh, where concentrations of arsenic can reach 1.00 mg per liter of water. If a person drinks 2.95 L of water per day, how many grams of arsenic would he or she ingest in a year?
1.08 g
Calculate the energy of a photon of electromagnetic radiation with a wavelength of 1404.5 nm.
1.41 x 10^-19 J
We need to use the Cr-Au galvanic cell to power a 75.0-watt light bulb. Please determine how long (in min) the galvanic cell will power the light bulb before running out power. The galvanic cell uses the following solutions: 0.810 L 1.50 M Cr2(SO4)3 solution and 1.20 L 0.860 M Au(NO3)3 solution. (refer to chart in screenshot) power(W) = electric potential(V) x current(A); charge(C)= current(A) x time(s); 1 mol of electrons = 96485 C
1.5 x 10^2 min
o draw a Lewis structure, first add the number of outer (valence) electrons contributed by each atom to obtain the total number of outer electrons. What is this value for a molecule of N2?
10
A curling iron with a resistance of 20.00 ohms is plugged into a 230.0 V power supply. How much current is flowing through the curling iron?
11.50 A 230.0/20.00=11.5
After 3 half-lives have passed, what % of the original radioactive isotope remains?
12.5%
What percentage of a radioactive isotope would remain after three half-lives?
12.5%
Calculate the wavelength of a photon of electromagnetic radiation with a frequency of 21.7 MHz. (1 MHz = 106 Hz, treat this conversion factor as an exact number)
13.80
The density of gold is measured to be 19.3 kg/L, which of the following is the correct expression of the density of gold in g/cm3?
19.3 g/cm3
Label the mass number and atomic number for the symbol of gold below. How many protons and neutrons are in the nucleus of this isotope of gold?
197 = mass number Au 79 = atomic number neutrons: 118 protons: 79
If 1.8 × 10^14 J is released in a nuclear reaction, how much matter was lost?
2.0 × 10^−3 kg *use E=mc^2 where c = 3.0 x 10^8 m/s 1.8 × 10^14 J=m(3.0 x 10^8)^2
What is the density of a block of material that is 12.0 cm × 6.00 cm × 2.00 cm and has a mass of 356 g?
2.47 g/cm3
The specific heat capacity if defined as the amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius (ºC). The specific heat of water is 1.0 calorie per gram per ºC. How many calories are required to raise the temperature of 2.00 grams of water by 10.0ºC?
20.0 cal
The mass of CO2 generated from burning 108 g of ethanol (C2H5OH) with extra amount of oxygen is:
206 g
When Pu-239 produces an alpha particle, which new isotope is produced?
235 U 92
Which of the following balances the nuclear equation of alpha decay seen below? 228Th --> 4He + ? 90 2
244Ra 88
If you have 200.0 g of radioisotope with a half-life of 5 days, how much isotope would remain after 15 days?
25.0 g *this is 3 half-lives, so 200/2=100 100/2=50 50/2=25.0
How many biodiesel molecules does one triglyceride produce?
3
Although it is not usually used, Einstein's equation, E = mc^2 applies to chemical reactions as well as nuclear reactions. A combustion reaction released 35.0 kJ when one gram of a reactant was burned. How much of this mass was lost in the process? 1 joule = 1 kilogram-meter^2/second^2
3.90 x 10^-10 g
Label the mass number and atomic number for the symbol of phosphorus below. How many protons and neutrons are in the nucleus of this isotope?
31 = mass number P 15 = atomic number neutrons: 16 protons: 15
If all of the ozone in a column of atmosphere were condensed into a thin layer and the layer was 3.51 mm thick at the standard temperature and pressure, the ozone concentration will be
351 DU
Yellow light has a wavelength of 580 nm. What is the frequency of this light?
5.2 × 10^14 s−1
The generator in our apartment building is burning gasoline (C8H18) to provide electricity for the residents. if we need it to provide 2534 kJ electric energy in total, the heat of combustion of gasoline is 5071.7 kJ/mole. The energy efficiency of generating electricity through combustion is 33.00%. The emitted CO2 will be:
533.1 g
How many neutrons are in 92Kr? 36
56 92-36=56
How many protons are in an atom of carbon?
6
The half-life of carbon-14 is 5730 years. If you started with 100.0 g of carbon-14, how much would remain after 4 half-lives?
6.25 g 100/2 = 50 50/2 = 25 25/2 = 12.5 12.5/2 = 6.25
To determine the hardness of a water sample, 25.5 mL of the water sample was titrated with EDTA solution. It took 11.6 mL of the EDTA solution to reach the end point of the titration. It turns out that the water sample contains 0.0034 M calcium ions. What was the molar concentration of EDTA used in this titration?
7.5 x 10^-3 M
What is the power of a light bulb powered by a battery with 3.0 V voltage and the current is 25 A? [hint: Electric potential(V) = Power (W)/Current (A)]
75 W 3.0 x 25 = 75
If we supply a current of 65 A for 25 minutes to an electrolytic cell to decompose water into H2 and O2 gas, how many grams of O2 will we produce? charge(C) = current(A) x time(s); 1 mol of electrons = 96485 C
8.1 g
Although coal is a complex mixture of substances, its elemental composition can be approximated by the formula C135H96O9NS. Using this chemical formula, calculate the percentage, by mass, of carbon (C) in coal.
85%
The quantity 8.7 × 10^5 g expressed in standard decimal notation.
870,000 g
What will be the current that a 1.2 m2 solar cell can produce in 8 hours? The sunlight intensity is 2.5 kWh/(m2·day). The useful sunlight wavelength is 525 nm for this solar cell. The efficiency of this solar cell is 18%.
9.5 A
EDTA titration was used to determine the hardness of a water sample, it turns out the water sample contains 81.8 ppm of MgCO3. What was the molar concentration of Mg2+ in the water sample? (1ppm=1mg/L)
9.70 x 10^-4 M
Which differentiates a compound from a mixture of two or more elements?
A compound does not exhibit the individual properties of the elements of which it is composed
Which substance has the highest pH? A sulfuric acid solution Orange juice Rain A lye solution
A lye solution
Which is a properly balanced reduction reaction? A. Al3+(aq) + 3e- --> Al(s) B. Al(s) --> Al3+(aq) + 3e- C. 3Al3+(aq) + 3e- --> Al(s) D. Al(s) --> 3Al3+(aq) + 3e-
A. Al3+(aq) + 3e- --> Al(s)
What element is used to dope an n-type semiconductor?
Arsenic *Silicon can't be doped with itself and only one of these has one more electron than silicon.
In this photovoltaic (solar) cell, the n-type semiconductor is in the region labeled
B (refer to screenshot)
Which reaction will proceed as a reduction reaction? A. Pb2+(aq) + 2e- --> Pb(s) B. Ag+(aq) + e- --> Ag(s)
B. Ag+(aq) + e- --> Ag(s)
Which is a properly balanced oxidation reaction? A. Li+(aq) + e- --> Li(s) B. Li(s) --> Li+(aq) + e- C. Li+(aq) + 2e- --> Li(s) D. Li(s) --> Li+(aq) + 2e-
B. Li(s) --> Li+(aq) + e-
Which of the following molecules absorbs IR light? He F2 BF3 Cl2
BF3
Determine the shape or geometry of SF2.
Bent
Which of the following statements is false about biofuels? Biofuel is absolutely carbon neutral because plants remove CO2 from the atmosphere during growth. Growing corns for biofuel contributes to the increase of food price. Ethanol(CH3CH2OH) releases less CO2 per mile compared to gasoline(C8H18). Sugar cane be converted into biofuels.
Biofuel is absolutely carbon neutral because plants remove CO2 from the atmosphere during growth
When we studied the properties of air we breathe in lab, bromothymol blue was used as an indicator to determine the presence of carbon dioxide in exhaled breath. Which of the following happened afther the exhaled air was bubbled through the indicator solution?
Bromothymol blue solution will turn from blue to yellow.
Which of the following pair molecules will not form hydrogen bond? CH2F2 (C is the central atom, all other atoms connect with C) and H2O NH3 and H2O CCl4 and H2O HF and NH3
CCl4 and H2O
All of these pollutants can be detected by their odors except
CO
Catalytic converters reduce the amount of _____ in car exhaust.
CO
Which component of the air makes up approximately 100 times more of an exhaled breath than of an inhaled breath?
CO2
Use the solubility table provided on the data sheet, which of the following reaction will produce a white precipitate?
Ca(NO3)2(aq) + Na2SO4(aq)
Identify of chemical species gets oxidized and which gets reduced in the following overall chemical reaction: 2Ca(s) + O2(g) â 2CaO(s)
Calcium is oxidized, whereas oxygen is reduced.
In general, which airborne material is not likely to be affected by the filters or indoor air handling equipment?
Carbon monoxide
Which of the following statements is false? Entropy is always increasing in the Universe. Catalysts speed up a chemical reaction by increasing its activation energy. A chemical reaction accompanied by an absorbing of energy is called an endothermic reaction. The energy needed to initiate a chemical reaction is called the activation energy.
Catalysts speed up a chemical reaction by increasing its activation energy.
Which product of the ultraviolet decomposition of CFCs acts as the catalyst for ozone decomposition?
Chlorine radicals
Which Lewis structure for formaldehyde (CH2O) is correct? (refer to screenshot)
D
How can we address climate change?
Develop a global policy to reduce carbon dioxide output, Find alternate energy sources, Planting trees
In the famous equation E = mc2, the symbols represent
E = energy, m = mass, c = speed of light
In lab, water was titrated with EDTA to determine the hardness, which of the following statements is true?
EBT indicator changed color from pink to deep purple at the end point of the titration.
Which statement is not true? Solution is a mixture. Electrolytes can be any water-soluble substances. Ice is less dense than water. Pure water does not conduct electricity.
Electrolytes can be any water-soluble substances.
When an atom absorbs visible radiation:
Electrons jump from lower energy levels to higher energy levels
Electrical energy is one of the primary types of energy that we consume. Renewable and non-renewable energy sources are all converted from their original form into electrical energy. Fill in the table with the original type of energy for each of the sources of renewable electric power.
Energy Source & Type of Energy to Convert: fuel cell--> chemical solar thermal --> heat wind --> kinetic hydroelectric --> kinetic geothermal --> heat solar photovoltaic -->
Which process plays the most important role in the greenhouse effect?
Energy radiated by the earth is absorbed by the atmosphere
An exothermic reaction is a reaction that absorbs heat from the surroundings.
False
In a nuclear reactor, control rods are used to supply neutrons and initiate more fission reactions.
False
In terms of electron transfer, oxidation is a gain of electrons.
False
The more toxic the pollutant, the higher the concentration is set when concerning air quality standards.
False
Which of the following statement is true? Frequency of a light is directly proportional to its speed. Frequency of a light is inversely proportional to its wavelength. Frequency of a light is inversely proportional to its amplitude. Frequency of a light is directly proportional to its wavelength.
Frequency of a light is inversely proportional to its wavelength.
Which covalent bond is the most polar? H — N H — O H — H H — S
H — O
Which of the following makes up an alpha particle? A. He-4 nucleus B. Electron C. Photon D. 2 Protons
He-4 nucleus
What is the correct description of generating electricity in a modern power plant?
Heat boils water to make steam, which drives a turbine
Which compound that is soluble in water, but when mixed with potassium iodide (KI) solution would form a precipitate?
Hg2(NO3)2
Hybrid vehicles are an increasingly popular way to conserve energy. Fill in the blanks in the sentences below about hybrid vehicles and how they work.
Hybrid vehicles use a combination of fossil fuels and battery power. The battery is charged by storing energy from braking that would usually be lost to friction. This energy conservation reduces the amount of carbon dioxide and other pollutants emitted by the car. Unlike gas only vehicles, hybrid vehicles often have better gas mileage for city driving than for highway driving.
Consider these three compounds. (refer to screenshot) Which are isomers?
I and III only
Which increases the efficiency of a photovoltaic or solar cell? I. Replacing crystalline silicon with its non-crystalline form II. Increasing the number of alternating p- and n-type layers of semiconductors III. Decreasing the thickness of each alternating p- and n-type layer of semiconductor
II and III only *There are many ways to increase efficiency, although they are not easy to accomplish in an industrial setting.
Radioisotopes can help or hinder our lives. Complete the sentences below about some interesting examples.
Iodine-131 is used for medical imaging, especially for diagnosing thyroid problems. Carbon-14 has half life of 5715 years. It is incorporated into living things and is useful for determining their age. Radon-222 is a product in the radioactive decay series of uranium. It is a gas which accumulates in basements, affecting the air quality in our homes. Uranium-238 has a very long half life of 4.5 billion years, so it is good for determining the age of rocks. Strontium-90 closely resembles calcium and will be incorporated into the boneswhen people who are exposed to it.
What is the effect of the absorption of infrared energy on matter?
It increases the vibration of chemical bonds
Which of the following is a unit of power? Joules/meter Joules/minute Joules/mole Joules/gram
Joules/minute
Predict the products of this reaction: KOH + HNO3 →
KNO3 + H2O
What sort of energy is associated with energy from wind?
Kinetic energy
Suppose we have two lamps that emit electromagnetic radiation. Light from lamp A has a wavelength of 524 nm and light from lamp B has energy of 6.68 x 10-19 J. Which of the following statement is true regarding these two lamps?
Light from lamp A has a lower frequency than light from lamp B.
In a solar cell, semiconductors of the p-type and n-type are placed in contact with each other via a conducting wire. In order to generate an electric current, which of the following must be true?
Light shining on the system must have enough energy to set electrons in motion from the n-type semiconductors to the p-type
Which of the following is a proper use for a calorimeter? Measuring heat of combustion Measuring entropy of a reaction Measuring the amount of oxygen consumed in a combustion reaction Measuring temperature of a mixture
Measuring heat of combustion
A standard alkaline battery gives an output of 1.5V. Would a lead/silver battery make a good replacement?
No, the voltage is too small.
Waste created at these power plants must be stored indefinitely
Nuclear plants
The sun is the most powerful, reliable energy source available on earth. As photovoltaic cells become more efficient, solar power is becoming a more realistic option for supplying our energy needs. Fill in the blanks in the sentences below about photovoltaic cells.
Photovoltaic cells (PVs) convert light energy into electrical energy. PVs are made from semiconductors. Two different types are layered - n-type semiconductors have extra electrons and p-type semiconductors need more electrons. Dopants such as gallium or arsenicare added to allow electrons to flow through the silicon semiconductor. When a photon with enough energy hits the PV, an "extra" electron is "knocked" from one layer into a "hole" in the other. The movement of electrons is an electrical current.
The primary and secondary coolants in a nuclear power plant have very different but equally vital roles. Label each type of coolant with its characteristics.
Primary coolant: heated directly by energy given off by nuclear fuel, will contain radioactive material, links the nuclear reactor to the rest of the power plant, aqueous boric acid absorbs radiation Secondary coolant: doesn't contact the reactor, fluid is cooled by a condenser and recycled, creates steam to turn a turbine and generate electricity
Give the number of protons and neutrons in the nucleus of 12C.
Protons: 6 Neutrons: 6
Which of the following is the largest natural source of ionizing radiation?
Radon gas
This is the photochemical reaction involved in photography: 2H2O(l) + 4 AgCl(s) + photon → 4Ag(s) + 4HCl(aq) + O2(g). Why do we use red light in photography darkrooms as a safelight to illuminate the work area?
Red light has less energy available for the reacion to occur.
Which pollutant is present in air as particulate matter?
Soot
Which of the following automotive energy storage devices would give rise to the fastest acceleration from zero to 60 mph?
Supercapacitors
The O2 molecule breaks apart at shorter wavelengths than the O3 molecule. What is the main reason for this? (Hint: Draw the Lewis structures.)
The average bond in O2 is shorter and stronger than that of O3.
A 0.25 M solution of the sugar sucrose, C12H22O11, in water is tested for conductivity using the type of apparatus shown. What do you predict will happen?
The bulb will not light up - sucrose is in the molecular form in aqueous solution
Which one is not the consequences of global warming?
The concentration of stratospheric ozone is declining.
What is the primary determinant of the voltage developed by a battery?
The nature of the materials in the reaction *There is no way to alter the voltage in a cell but to use different anode and cathode
What distinguishes the atoms of one element from another?
The number of protons
How do mineral nanoparticles in sunscreens protect from UV radiation?
The particles absorb incoming UV light
K → K+ + e−
This half-reaction represents the process of oxidation because electrons are lost
A chain reaction is a self-sustaining reaction where the products become reactants and allow the reaction to continue.
True
Your experiment will under-estimate the actual heat of combustion because some of the heat energy from the reaction will be lost to the surroundings.
True
When dissolved in water, hydrogen bromide (HBr) forms a strong acid named as hydrobromic acid. Determine the hydroxide ion concentration in a 4.50 L solution containing 3.78 g hydrogen bromide; Kw = 1.00 × 10^−14 at 25C.
[OH-] = 9.63 × 10^−13 M
The "doping" of a semiconductor to improve its performance means
adding small amounts of other elements to the pure semiconductor to change the freedom of electron motion throughout the crystal
What type of radiation is given off in this nuclear reaction? 210 206 Po --> Pb + ? 84 82
alpha radiation *Remember that the masses and atomic numbers must be the same of both sides of the equation.
A major advantage of a fuel cell over a standard battery is that
as long as oxygen and fuel are supplied, a fuel cell will not run down like a battery will *Remember that batteries must be recharged and that nothing is 100 percent efficient
The greenhouse effect refers to the process by which
atmospheric gases trap and return infrared radiation radiated by Earth.
Light behaves like
both a particle and a wave
Given this diagram, this semiconductor is A. made of pure silicon. B. carrying an extra electron. C. missing an electron. D. excited by a photon.
carrying an extra electron. (refer to screenshot) *Notice the electron environment around the doped atom.
Currently, the primary source of sulfur dioxide emissions into the atmosphere is
coal burning power plants.
A recent set of advertisements has a picture of an aluminum can with an aluminum-frame bicycle, along with a hypothetical quote from the can that reads: "I want to be a bike. Recycle me." The analysis of the life cycle of an item starting with its raw materials and ending with the used item becoming the raw material for new products is called
cradle-to-cradle.
Silicon has four electrons in its outer energy level, gallium has three. Adding small amounts of gallium to pure silicon
creates a p-type semiconductor *n-type semiconductors are doped with elements that have five valence electrons.
N2O5 is the chemical formula for
dinitrogen pentoxide.
What is the reason that the heat of combustion of ethanol (C2H5OH, 1360 kJ/mol) is smaller than the heat of combustion of propane (C3H8, 2219 kJ/mol)?
ethanol contains oxygen, as a fuel, it is partially oxidized.
In a refinery, the components of petroleum are separated by
fractional distillation.
Which of the following hydrocarbons has the highest boiling point? propane ethane hexane butane
hexane
From ice core data, we can estimate the temperature of the earth dating back hundreds of thousands of years. Which of the following would indicate a cold temperature?
higher ratio of 1H2O to 2H2O in ice core
Free radicals are
highly reactive chemical species. species with unpaired electrons. species such as H• and •OH.
Which practices might be described as carbon sequestration? i. Planting trees ii. Deforestation iii. Pumping carbon dioxide deep into the ocean iv. Increasing combustion of fossil fuels
i and iii only
Chlorofluorocarbons rise to the stratosphere and
interact with UV light to produce free radicals to destroy ozone.
Semiconductors, such as the element silicon, may be used in cells that convert solar radiation to electricity. One of the major difficulties encountered in using silicon is that it
is expensive to produce large quantities of extremely pure silicon *The purity of silicon needed to make semiconductors is very high.
Which unit is commonly used by utilities to measure the amount of electrical energy consumed?
kWh
Matter is anything that occupies space and has a __________.
mass
What is the oxidation state of the metal in the compound: CaCl2
metal in compound is Ca and charge is +2
A(n) __________ is a fixed number of atoms held together by chemical bonds in a certain spatial arrangement.
molecule
Dichlorodifluoromethane(CCl2F2) is one of the CFC molecules, which of the following vibrational mode will not absorb IR radiation? (note: all chlorine and fluorine atoms are directly connect to carbon atom.) symmetric stretching asymmetric stretching bending none of the above
none of the above
In reference to waves, frequency is the
number of waves passing a fixed point in one second.
Combustion is a chemical process in which a fuel combines with __________ to release energy and form products.
oxygen
Which of the following is not part of the Chapman cycle in the stratosphere?
ozone is removed by its reaction with natrual gas.
Sunlight (solar radiation) may be turned directly into electricity using __________ cells.
photovoltaic
When the __________ molecules of ethanol, C2H5OH, are added to water, the ethanol molecules __________.
polar; form hydrogen bonds with the polar water molecules
The nucleus of an atom contains
protons and neutrons only
Nickel-cadmium batteries are common rechargeable batteries used in a variety of small electronic devices. Based upon the overall cell reaction, label this simple galvanic cell.
refer to screenshot
At water treatment plants aluminum sulfate and calcium hydroxide are added to
remove suspended clay and dust particles.
Which of the following states of matter has a definite shape?
solid
Fission is the process of creating energy by
splitting large nuclei to form smaller, more stable nuclei
In the properies of air we breathe lab, it took about 471 s for air to change the bromothymol blue solution color, but only 82 s for the exhaled air. The observation demonstrated that
the concentration of carbon dioxide in the exhaled air is much higher than air.
The reason that the bond angle in water is smaller than the bond angle in ammonium is
the repulsion from lone pair electrons is stronger in water than in ammonium.
Neither N2 nor O2 are greenhouse gases because
their overall electric charge distribution does not change when they vibrate
The main reason that water supplies are chlorinated is
to kill disease-causing organisms in the water.
The Montreal protocol is a
treaty to reduce the amount of CFCs produced in the world
If we assume that the top of Mt. Everest is the highest land mass on earth, hikers who scale its summit are standing in the
troposphere.
Ozone is considered an air pollutant in the __________ but is a valuable protective layer in the __________.
troposphere; stratosphere
A polar covalent bond is created when
two atoms share their bonding electrons unequally
