PAST BOARDS Flashcards
Calculate the mass of the Sun using the fact that the period of the Earth’s orbit around the Sun is 3.156x107 s and its
distance from the Sun is 1.496x1011 m.
1.99x1030 kg
What is the theory in two- or three-dimensional collision to be applied when playing billiards and in order to sink the target ball in the corner pocket?
Where two equal masses undergo a glancing elastic collision.
If the normality of HCl is greater by 10% compared to KOH estimate the normality of the HCL solution when 0.67 grams
of (NH4)2 SO4 is dissolved in water, treated with excess NaOH and the ammonia released is passed through a solution
of 20 ml of HCl. The excess acid solution is titrated using 15.01ml of KOH solution.
0.152 N
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.
9.3 mg/L
Number of double bonds in geraniol
2
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)?
16.7 mg/L
Tritium (3H) decays by beta emission to 3He with a half-life of 12.26 years. A sample of a tritiated compound has an initial activity of 0.833 Bq. Calculate the number Ni of tritium nuclei in the sample initially, the decay constant k, and the activity after 2.50 years.
4.7x108 nuclei, 1.8x10-9/s, 0.72 Bq
The removal of phosphorus to prevent or reduce
eutrophication is typically accomplished by chemical
precipitation using one of three compounds. Balance the precipitations reactions for each are shown here.
Using lime: Ca(OH)2 + HPO4 = Ca5(PO4)3OH + H2O + OH-
Using alum: Al2(SO4)3 + HPO42- = AlPO4 + H+ + SO42-
Using ferric chloride: FeCl3 + HPO42- = FePO4 + H+ + Cl-
5, 3, 1, 3, 6; 1, 2, 2, 2, 3; 1, 1, 1, 1, 3
Which of the following physical properties differ for each of a pair of enantiomers?
A. Boiling point and melting point
B. Direction of rotation of plane-polarized light
C. Index of refraction
D. Solubility in ethanol
Direction of rotation of plane-polarized light
If the age of the Earth is 1.3x1017 years, what is the
approximate age of the universe?
5 x 10^17 years
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.
1.46 mg/L
Estimate the number of breaths taken during an average life span.
4 x 10^8 breaths
The free neutron is an unstable particle that decays into a proton. What other particle is formed in neutron decay, and
what is the maximum kinetic energy (in MeV) that it can possess?
electron, 0.78 MeV
Suppose a long-chain polypeptide is constructed entirely from phenylalanine monomer units. What is its empirical formula? How many amino acids does it contain if its molar mass is 17,500 g/mol?
119
On your wedding day your lover gives you a ring of mass 3.80 g. Fifty years later its mass is 3.35 g. On the average, how many atoms were abraded from the ring during each second of your marriage?
8.7x1011
The three naturally occurring isotopes of uranium are 234U
(half-life 2.5x105 years), 235U (half-life 7.0x108 years), and 238U (half-life 4.5x109 years). As time passes, will the average atomic mass of the uranium in a sample taken from nature increase, decrease, or remain constant?
increase
The activation energy for the isomerization reaction of CH3NC in is 161 kJ/mol, and the reaction rate constant at 600 K is
0.41/s. Calculate the Arrhenius factor and the rate constant for this reaction at 1000 K.
4.3x10-3, 1.7x105/s
The Alangilan Barangay Council in Batangas City has asked you to determine whether the discharge of the barangay’s wastewater into the Calumpang River will reduce the DO below
the standard of 5.00 mg/L at Poblacion 5.79 km downstream, or at any other point downstream. The pertinent data are as
follows:
Calculate the dissolved oxygen at Poblacion.
4.77 mg/L
A pail of water is rotated in a vertical circle of radius
1.00 m. What is the minimum speed of the pail at the top of the circle if no water is to spill out?
3.13 m/s
Which of the following functional groups is present in the melamine molecule?
Amine
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 = d22/d12, calculate the intensity of radiation at the distance of two meters
when the intensity of radiation is 29 millicurie at a one meter distance.
7 mCi
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).
The addition of energy in the form of sunlight drives
the equilibrium to the right and its removal drives the
equilibrium to the left,
Of the following pairs of physical systems, determine the one with the greater chemical potential.
(1A); one mole of H2O (l) at 100.1 degC; or (B); one mole of H20 (g) at 102 degC. (2A); ten grams of Fe at 2 degC or (2B) ten grams of Fe at 36 degC. (3A); 25 liters of air at 1 atm pressure or (3B) the same
amount of air compressed isothermally to 100 atm.
1B, 2A, 3B
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.
first