Preboards May 2023

Question 1

How many moles of H2 are required to completely reduce 15 grams of the unsaturated hydrocarbon?
CH2=CHCH2CH=CH2 + 2H2= CH3CH2CH2CH2CH3

Answer 1

0.442 mol H2

Question 2

Biochemical compounds are either hydrophilic, hydrophobic or amphipathic. Classify the following compounds: glucose, stearic acid, soaps, fatty acids

Answer 2

Hydrophilic, amphipathic, amphipathic, hydrophobic

Question 3

popular chemical demonstration is the “magic genie” procedure, in which hydrogen peroxide decomposes to water and oxygen gas with the aid of a catalyst. The activation energy of this (uncatalyzed) reaction is 70.0 kJ/mol. When the catalyst is added, the activation energy (at 20degC) is 42.0 kJ/mol. Theoretically, to what temperature (degC) would one have to heat the hydrogen peroxide solution so that the rate of the uncatalyzed reaction is equal to the rate of the catalyzed reaction at 20degC? Assume the frequency factor A is constant, and assume the initial concentrations are the same.

Answer 3

215degC

Question 4

Alcohols, phenols, and carboxylic acids all contain an OH group. Which are the strongest acids? Which are the weakest acids?

Answer 4

carboxylic acid – strongest, phenol – weaker, alcohol - weakest

Question 5

Propanoic acid and methyl acetate are constitutional isomers, and both are liquids at room temperature. One of these compounds has a boiling point of 141°C; the other has a
boiling point of 57°C. Which compound has a higher boiling point?

Answer 5

propanoic acid

Question 6

One of the few industrial-scale processes that produce organic compounds electrochemically is used by the Monsanto Company to produce 1,4-dicyanobutane. The reduction reaction
is 2 CH2 = CHCN + 2H+ + 2e- –> NC-(CH2)4-CN
The NC-(CH2)4-CN is then chemically reducing using hydrogen gas to H2N-(CH2)6-NH2, which is used in the production of nylon. what current must be used to produce 150 kg NC-(CH2)4-CN per hour?

Answer 6

74400 A

Question 7

Predict whether each of the following nuclides is stable or unstable (radioactive). If the nuclide is unstable, predict the type of radioactivity you would expect it to exhibit. 45K, 56Fe, 11Na, 194Tl.

Answer 7

unstable-beta production, stable, unstable-positron production, unstable-alpha production

Question 8

Consider a weak acid, HX. If a 0.10-M solution of HX has a pH of 5.83 at 25degC, what is change in Gibbs energy for the acid’s dissociation reaction at 25degC?

Answer 8

6 kJ/mol

Question 9

If you had a mole of U.S. dollar bills and equally distributed the money to all of the people of the world, how rich would every person be? Assume a world population of 7 billion.

Answer 9

90 trillion dollars

Question 10

A rock contains 0.688 mg 206Pb for every 1.000 mg 238U present. Assuming that no lead was originally present, that all the 206Pb formed over the years has remained in the rock, and that the number of nuclides in intermediate stages of decay between 238U and 206Pb is negligible, calculate the age of the rock.

Answer 10

3.8x10^9 years

Question 11

Whatever the compound, the gram molecular weight contains the same number of molecules, known as Avogadro’s number. It is expressed as:

Answer 11

6.02x10^23 particles per mole

Question 12

Assume that you could track a single aluminum beverage can (with a mass of 16 g) through several cycles of reclamation and that a 10% “loss” occurred in each recovery cycle. How much new aluminum must be supplied to replace the loss at the end of the third reclamation?

Answer 12

4.3 g

Question 13

The isotope of an unknown element, X, has a mass number of 79. The most stable ion of the isotope has 36 electrons and forms a binary compound with sodium having a formula of Na2X. Which of the following statements is(are) true?
I. The binary compound formed between X and fluorine will be a covalent compound.
II. The isotope of X contains 38 protons.
III. The isotope of X contains 41 neutrons.
IV. The identity of X is strontium, Sr.

Answer 13

I only

Question 14

A chemical analysis has revealed the following composition for the rain falling on the city of Thule.
1.38 mg · L^−1 HNO3
3.21 mg · L^−1 H2SO4
0.354 mg · L^−1 HCl
0.361 mg · L^−1 NH3
What is the pH of the rainwater?

Answer 14

4.12

Question 15

Bacterial cells have been represented by the chemical formula C5H7NO2. Compute the theoretical oxygen demand (in grams O2 · mol^- of cells), assuming the following reactions apply.

Answer 15

224

Question 16

A sewage lagoon that has a surface area of 10 ha and a depth of 1 m is receiving 8640 m^3 d^- of sewage containing 100 mg · L^- of biodegradable contaminant. At steady state, the effluent from the lagoon must not exceed 20mg· L^- of biodegradable contaminant. Assuming the lagoon is well mixed and that there are no losses or gains of water in the lagoon other than the sewage input, what biodegradation reaction rate coefficient (d^-) must be achieved for a first-order reaction?

Answer 16

0.35

Question 17

An electron in a hydrogen atom is excited from the ground state to the n = 4 state. Comment on the correctness of the following statements (true or false).
(a) n = 4 is the first excited state.
(b) It takes more energy to ionize (remove) the electron from n = 4 than from the ground state.
(c) The electron is farther from the nucleus (on average) in n = 4 than in the ground state.
(d) The wavelength of light emitted when the electron drops from n = 4 to n = 1 is longer than that from n=4 to n=2.
(e) The wavelength the atom absorbs in going from n=1 to n=4 is the same as that emitted as it goes from n=4 to n=1.

Answer 17

F, F, T, F, T

Question 18

An ethylene molecule has a total of ___ sigma bonds.

Answer 18

5

Question 19

How to differentiate alkane alkene and alkyne?

Answer 19

reaction with Br2

Question 20

Can a hydrogen bond form between
a) Two molecules of methanol, CH3OH?
b) Two molecules of formaldehyde, CH2O?
c) One molecule of methanol, CH3OH, and one of formaldehyde, CH2O?

Answer 20

Yes, No, Yes

Question 21

Glucose is the only carbohydrate compound that the brain can use for energy. Which pathway is mobilized to supply the need of the brain during starvation?

Answer 21

gluconeogenesis

Question 22

Which amino acid has the highest percentage nitrogen (g N/100 g amino acid)?

Answer 22

Arginine

Question 23

Which of the following is true about sunscreen and sunblock between sunblock and sunscreen?

Answer 23

A sunscreen prevents a portion of ultraviolet radiation from reaching protected screen.

Question 24

Is it possible for an endothermic reaction to have zero activation energy?

Answer 24

No

Question 25

How many carbon atoms in olvanil?

Answer 25

26

Question 26

Leaded gasoline contains an additive to prevent engine “knocking.” On analysis, the additive compound is found to contain carbon, hydrogen, and lead (Pb) (hence, “leaded gasoline”). When 51.36 g of this compound are burned in an apparatus, 55.90 g of CO2 and 28.61 g of H2O are produced. Determine the empirical formula of the gasoline additive.

Answer 26

PbC8H20

Question 27

Pentane has three structural isomers: (A) n-pentane, (B) neopentane, and (C) isopentane. Arrange these isomers in increasing boiling point.

Answer 27

B < C < A (Perrys T2-5)

Question 28

Suppose that we have a stain on an oil painting that we want to remove without damaging the painting. The stain is not water-insoluble. Knowing the polarities of the following solvents, which one would we try first: benzene, isopropyl alcohol, hexane

Answer 28

isopropyl alcohol

Question 29

Which element is difficult to remove from sewage and wastewater and at the same time, it contributes to bacterial and algae overgrowth in freshwater?

Answer 29

nitrogen

Question 30

There are approximately 20 amino acids in human protein. Name 3 essential amino acids:

Answer 30

Arginine, lysine, phenylalanine

Question 31

An experimental electric jeepney running in Makati on 12V battery at 20 m/s has a total energy storage of 2.0x10^7 Joules. If 8.0 KW is needed to move the vehicle, what is the quantity of energy supplied to the motor and how far will it travel?

Answer 31

667 A, 50km

Question 32

Determine the value of the rate constant at 410 K for a reaction with rate constant of 3.101 x 101sec^-1 at 430 K and an activation energy of 86.52 KJ/mole.

Answer 32

9.54 x 10^0

Question 33

An air jet operates at 2,500 rev/min and uses 7.89 x 10^3J of energy and exhausts 4.58 x 10^3 J for each crankshaft revolution. Determine the quantity of gasoline fuel consumed in one hour of operation if the heat of combustion is 4.03 x 10^7 J/liter.

Answer 33

29.4 L/hr

Question 34

How do two free radicals react when they encounter each other?

Answer 34

They unite with covalent bond formation

Question 35

Determine the stability of the atmosphere given the following data collected for Tagaytay:

Answer 35

-1.02 degrees C per 100 meters

Question 36

A city in Laguna generate 0.96 kilograms/capita per day of municipal solid waste (MSW. Makati City in Metro Manila generates 1.9 kilograms per capita per day of MSW. If both cities have a population of 20000 inhabitants, determine the following: (a) amount of MSW generated in each city; (b) number of trucks needed to collect the MSW twice weekly, if each truck has a capacity of 4.4 tons and operates 5 days per week. Two loads per day at 75% capacity is the travel quota per day. (c) the number and volume of MSW in tons that enter the landfill.

Answer 36

19100 and 39000 kg/d; 4 and 8 trucks; 58 and 105 m^3/d

Question 37

Are the following processes exothermic or endothermic? a) When solid KBr is dissolved in water, the solution gets colder. b) Natural gas (CH4) is burned in a furnace. c) When concentrated H2SO4 is added to water, the solution gets very hot. d) Water is boiled in a teakettle.

Answer 37

endothermic, exothermic, exothermic, endothermic

Question 38

A 150.0-g sample of a metal at 75.0degC is added to 150.0 g H2O at 15.0degC. The temperature of the water rises to 18.3degC. Calculate the specific heat capacity of the metal, assuming that all the heat lost by the metal is gained by the water.

Answer 38

0.25 J/g-degC

Question 39

The best solar panels currently available are about 19% efficient in converting sunlight to electricity. A typical home will use about 40 kWh of electricity per day. Assuming 8.0 hours of useful sunlight per day, calculate the minimum solar panel surface area necessary to provide all of a typical home’s electricity.

Answer 39

25 m^2

Question 40

Arrange the following in order of increasing radius and increasing ionization energy: N+, N, N-

Answer 40

Radius: N+ < N < N-, Ionization Energy: N- < N < N+ (Remember MARB IEE)

Question 41

Predict which bond will be the most polar. COF, SiOF, GeOF

Answer 41

Ge-F

Question 42

A power plant in Benguet is burning coal on a cold clear January at 8:00 am with a wind speed of 2.6 meters/second measured at an elevation of 31 meters and an inversion layer with its base founded at a height of 695 meters. The effective height of the stack is 31 meters. Calculate the distance downward at which the plume released will reach the inversion layer and start to mix downward.

Answer 42

5.82 km

Question 43

If the initial density of bacteria is 10^4 cells per liter at the end of the accelerated growth phase, what is the number of bacteria after 25 generations?

Answer 43

3.4x10^11 cell L^-

Question 44

What compound is a ketone but it is not a carbohydrate but is useful commercially?

Answer 44

acetone

Question 45

Which Republic Act is the PRC Modernization Act of 2000?

Answer 45

R.A. 8981

Question 46

The discharge pipe from a sump pump in the dry well of a sewage lift station did not drain properly and the water at the discharge end of the pipe froze. A hole has been drilled into the ice and a 200-W electric heater has been inserted in the hole. If the discharge pipe contains 2 kg of ice, how long will it take to melt the ice? Assume all the heat goes into melting the ice.

Answer 46

56 min

Question 47

Calculate the entropy change if 350 g of water at 50C is mixed with 500 g of water at 700C.

Answer 47

4.49 eu

Question 48

The heat of combustion of methane, the major component of natural gas, is 213 kcal/mol. The heat of combustion of propane, the major component of LPG or bottled gas, is 530 kcal/mol. On a kcal/mol basis, which of these two fuels is the better source of heat energy? On a kcal/g basis, which of these two fuels is the better source of heat energy?

Answer 48

propane, methane

Question 49

How many moles and molecules are there in aspirin with a mass weight of 0.052 grams?

Answer 49

2.77 x10^ -3 moles C9H8O4 and 1.67 x10^23 molecules

Question 50

Classify these as kinetic or potential energy (1) Water held by a dam (2) A speeding train (3) A book on its edge before falling (4) A falling book (5) Electric current in a light bulb

Answer 50

potential, kinetic, potential, kinetic, kinetic

Question 51

We heat 50.0 g of an unknown substance by adding 205 cal, and its temperature rises by 7.0°C. Identify the substance.

Answer 51

ethanol

Question 52

Balance the chemical equation given K4Fe(CN)6 + H2SO4 + H2O = K2SO4 + FeSO4 + (NH4)2SO4 + CO

Answer 52

1,6,6,2,1,3,6

Question 53

When the same amount of solid iodine is added to the two identical glass tubes, stoppered and then heated to the same temperature, it was observed that the color in the two tubes is seen to be the same and solid iodine is still present in the bottom of the tubes. If a lot of additional iodine crystals are added to one of the tubes, is (are) there any charge(s).

Answer 53

the color of the vapor in that tube will become darker.

Question 54

Applying the Octet Rule, determine how many electrons each must each atom gain or lose to acquire an electron configuration identical to the noble gas nearest to it in atomic number; Sr, s and Si;

Answer 54

krypton; argon; argon and neon

Question 55

Determine the half-life of the decay process for a sample of Curium-243 when analysis showed that the activity of the sample decreased to 2923 disintegrations per second from the original 3011 dps.

Answer 55

K = 0.2x10^-1 yr^-1; t1/2 = 28.6 yr

Question 56

A chemical plant chemist working in the Pasig River Area was given the task to determine which of the two acid solutions can be discharged to the Pasig River with minimal effect on the river water. The chemist analyzed 0.1M solutions of the acetic acid (HAc) with Ka of 1.81 x 10^-5 and hydrofluoric acid (HF) with Ka of 6.6 x 10^-4. Which acid solution can be discharged?

Answer 56

HAc

Question 57

Match the radioactive isotope with its proper use: Cobalt-60

Answer 57

Cancer therapy

Question 58

Match the radioactive isotope with its proper use: Thallium-201

Answer 58

Heart scan in exercise

Question 59

Match the radioactive isotope with its proper use: Tritium

Answer 59

measure water content of body

Question 60

Match the radioactive isotope with its proper use: Mercury-197

Answer 60

Kidney scan

Question 61

Tetrafluoroethylene is the starting material for the production of poly(tetrafluoroethylene), a polymer that is widely used for the preparation of nonstick coatings on kitchenware. The most widely known trade name for this product is Teflon. Does tetrafluoroethylene have polar bonds? Is it a polar molecule? Does it have a dipole?

Answer 61

Yes, No, None

Question 62

Define is DNA? RNA?

Answer 62

Deoxyribonucleic acid and ribonucleic acid

Question 63

Are galvanic cells and electrolytic cells the same? Why?

Answer 63

No, because the galvanic cells electrochemical cells in which chemical cells occurs spontaneously; while in electrolytic cells, the chemical reaction is caused by externally applied potential difference.

Question 64

Balance the following equations: l (s) + HCl (aq) ------> AlCl3 (s) + H2 (g) C2H2(g) + O2 (g) ------> CO2 (g) + H2O (l)

Answer 64

2, 6, 2, 3; 2, 5, 4, 2

Question 65

A landfill that is 12 ha in area has a liner of thickness 0.9 m. Each year 1700 m3 of leachate is collected. The hydraulic conductivity of the liner is 3.9x10-10 m s-. What is the head of water above the liner?

Answer 65

1.04 m

Question 66

Determine the stoichiometric air-to-fuel ratio for C7H13. Ignore constituents other than oxygen and nitrogen in air and ignore the oxidation of nitrogen to nitrogen oxides.

Answer 66

14.5

Question 67

Morphine is a narcotic pain reliever used to treat moderate to severe pain. What is its chemical formula?

Answer 67

C17H19NO3

Question 68

Which will dissolve faster in coffee?

Answer 68

granular sugar in hot coffee

Question 69

An industrial pollutant to a river flowing with a velocity of 0.5 m/s. At this point in the river, the concentration of the pollutant is 50 ppm. The pollutant follows first order degradation with a rate constant equal to 0.35 hr^-1. What will be the concentration of the pollutant in the river when it reaches a city 12 km from the industrial plant?

Answer 69

4.85 (note: degradation)

Question 70

Which of the following objects are chiral (assume that there is no label or other identifying mark)? a) Pair of scissors b) Tennis ball c) Paper clip d) Beaker e) The swirl created in water as it drains out of a sink or bathtub

Answer 70

chiral, achiral, achiral, achiral, chiral

Question 71

An environmental engineering student was very interested in the reaction of the chemical 2,4,6-chickenwire. She went into the lab and found that 2,4,6-chickenwire degrades in water. During her experiments she collected the data in the following table. Determine if the reaction is zero-, first-, second-, third-order with respect to the concentration of 2,4,6-chickenwire.

Answer 71

first

Question 72

Tritium is used in glowing exit signs located where there is no electricity for light bulbs. If the half-life of tritium is 12.26 years, what percentage of the original quantity of the isotope is left in the sign after 18.5 years?

Answer 72

35.1%

Question 73

Which of the following functional groups is present in the melamine molecule?

Answer 73

amine

Question 74

A tannery with a wastewater flow of 0.011 m3/s and a BOD5 of 590 mg/L discharges into the Antamok Creek in Benguet. The creek has a 10-year, 7-day low flow of 1.7 m3/s. Upstream from the tannery, the BOD5 of the creek is 0.6 mg/L. The BOD rate constants are 0.115/day for the tannery and 3.7/day for the creek. The temperature of both the creek and the tannery wastewater is 20 deg C. Calculate the initial ultimate BOD after mixing.

Answer 74

9 mg/L

Question 75

Neohetramine, C16H21ON4 (285.37g/mol), is a common antihistamine. A 0.1247-g sample containing this compound was analyzed by the Kjeldahl method. The ammonia produced was collected in H3BO3; the resulting H2BO3 - was titrated with 26.13 mL of 0.01477 M HCl. Calculate the percentage of neohetramine in the sample.

Answer 75

22.08%

Question 76

What is the chemical formula and molecular weight of 11- tetradecenyl acetate?

Answer 76

C16H30O2, 254 g/mol

Question 77

Angelic acid occurs in symbol root, an herb used as a stimulant. What is the IUPAC name of angelic acid?

Answer 77

2-Methylbut-2-enoic acid

Question 78

Methanation is a unit process which converts CO and H2, in the presence of a catalyst, to methane. The product mixture of this process is called:

Answer 78

Marsh gas

Question 79

What is the mole fraction of the solute in a 1 m aqueous solution?.

Answer 79

0.0177

Question 80

__________ proposed that small particles of matter may at times display wave-like properties.

Answer 80

Louie De Broglie

Question 81

What is the chemical formula of alar?

Answer 81

C6H12NO3

Question 82

When charcoal is burned in a limited supply of oxygen in the presence of a mixture of H2O and other noncombustible gases (mostly CO2) is obtained. Such a mixture is called “synthesis gas”. This gas can be used to synthesize organic compounds, or it can be burned as a fuel. A typical synthesis gas consists of 55.0% CO, 33.0% H2 and 12.0% noncombustible gases (mostly CO2), by volume. To what temperature can 25.0 kg water at 25.0 0C be heated with the heat liberated by the combustion of 0.205 m3 of this typical synthesis gas, measured at 25.0 0C and 102.6 kPa pressure? Listed below are the formation enthalpies of the compounds of interest.

Answer 82

37 degC

Question 83

Most of the atmospheric air pollutants are present in large quantity in

Answer 83

troposphere (remember The Smart Man Takes Elevator)

Question 84

What is the color of lead chromate?

Answer 84

Yellow

Question 85

A magician rotates a pail of water in a vertical circle with a radius of 0.50 meter amazes the audience because no water spilled out. What is the minimum speed at which no water will spill out?

Answer 85

3.13 m/sec/2

Question 86

Which of the following physical properties differ for each of a pair of enantiomers?

Answer 86

Direction of rotation of plane-polarized light

Question 87

What is the distance of the earth to most remote quasar, distance of the earth to most remote known galaxies?

Answer 87

1.4x10^26

Question 88

What is the distance of the earth to most remote normal galaxies?

Answer 88

9.0x10^25

Question 89

What is the mean orbit radius of the earth about the sun?

Answer 89

1.50x10^11

Question 90

What is the distance of Earth to the nearest remote galaxy?

Answer 90

2.0x10^22

Question 91

Which among the following is the most abundant isotope of hydrogen?

Answer 91

Protium

Question 92

Which element has the highest percentage by mass in seawater?

Answer 92

Chlorine

Question 93

For all adiabatic processes, the entropy change of the system must be zero. (T or F)

Answer 93

False

Question 94

For one component system, it is possible for two phases in equilibrium to have different chemical potentials. (T or F)

Answer 94

False

Question 95

The change in Gibb’s free energy can be negative for a cyclic process. (T or F)

Answer 95

False

Question 96

A condition for equilibrium is that(ΔA) T, F =0 (T or F)

Answer 96

False

Question 97

A flowing stream has an oxygen deficiency of 6 mg/L. However, miles downstream the deficiency was reduced to 4 mg/L through atmospheric absorption. If the stream has a velocity of 2 mph and contains no BOD and other stream conditions are uniform through its length, estimate the oxygen deficit some 35 miles downstream from the original point.

Answer 97

1.46 mg/L

Question 98

In a solution supersaturated with CO3-2 and Ca2, what is the final concentration of Ca+2 per liter of solution at equilibrium Ksp CaCO3 (s) = 8.30 (use the quadratic formula)?

Answer 98

16.7 mg/L

Question 99

Why does the use of sunglasses with adjustable shading a practical illustration of the Le Chatelier’s principle? (Silver chloride is the compound used in the glasses, which upon exposure to sunlight produces silver Ag and chlorine Cl2).

Answer 99

Any of these (The addition of energy in the form of sunlight drives the equilibrium to the right and its removal drives the equilibrium to the left, since the more metal is produced, the darker the glasses; when external stress is applied to a system in equilibrium, which in this case refers to the production of silver metal which causes a change in the shade of the sunglasses; the changes in temperature cause the exothermic or endothermic reaction of the silver metal production to shift from left to right or vice-versa, thus causing the shades to change.)

Question 100

A sample of chromite is analysed to contain 30% CrO3. The sample is later fused with Na2O2 and dissolved in acid. If the sample weighs 0.20 gm, estimate the weight in grams of FeSO4 (NH4)2 SO4 6H2O that has to be added so that 15 millilitres of K2Cr2O7 solution are used, 0.20 millimole of Cr is present in the K2Cr2O7 solution.

Answer 100

4.458

Question 101

Of the following pairs of physical systems, determine the one with the greater chemical potential. a) (1A); one mole of H2O (l) at 100.1 degC; or (B); one mole of H20 (g) at 102 degC.

Answer 101

1B

Question 102

Of the following pairs of physical systems, determine the one with the greater chemical potential. b) (2A); ten grams of Fe at 2 degC or (2B) ten grams of Fe at 36 degC.

Answer 102

2B

Question 103

Of the following pairs of physical systems, determine the one with the greater chemical potential. c) (3A); 25 liters of air at 1 atm pressure or (3B) the same amount of air compressed isothermally to 100 atm.

Answer 103

3B

Question 104

Estimate the weight in grams of available hydrogen present in an organic acid of 20 ml of NaOH is needed to neutralize the acid. Given: 1 ml = 0.20 ml sulphuric acid (HSO3.NH2).

Answer 104

3.60 x 10^-4

Question 105

Applying the combined gas laws, determine the volume of 1.00 mole of Ne (g) at the temperature of 25 deg C and a pressure of 1 atm.

Answer 105

24.51 liters

Question 106

Determine the boiling point and freezing points; vapor pressure at 23 deg C of pure benzene, and a solution of benzene in 1.202 gms of naphthalene in 25.63 grams benzene; the molality and osmotic pressure of the solution.

Answer 106

81 deg C, 3.6 deg C; 83.6 mmHg; 0.32 M. 7.78 atm

Question 107

If one millieCurie is equal to 3.7 disintegrations/second and the intensity of any radiation decreases with the square of the distance from the source (I1/I2 = d2^2/d1^2, calculate the intensity of radiation at the distance of two meters when the intensity of radiation is 29 millicurie at a one-meter distance.

Answer 107

7 mCi

Question 108

In the metal planting plants in Cagayan de Oro and Iligan, the waste contains 20 mg/L of Cu^2+. It was decided that no precipitate most of copper in water, Ca(OH)2 will be used, until only 0.5mg/L of Cu remains. Estimate the hydroxide concentration in moles/liter needed to accomplish this.

Answer 108

1.6x10^-7 mol/liter

Question 109

Are reversible processes frictionless? Why?

Answer 109

because when reversed, retraces its forward path and restores the initial state of the system and surroundings.

Question 110

If radon-222 disintegrates to a stable condition by emitting three alpha emission and two beta emission, determine the nucleus formed

Answer 110

210Pb82