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PIMSO 2022 - Science - Senior Secondary - National Round

Question 1

The following image shows the phylogenetic tree generated from a subset of rodent species. Which of the following statements is therefore not true regarding rodent evolution?

Question illustration
  1. The rodent species form a polyphyletic group.
  2. Common ancestor of Rhynchomys soricoides and Mus musculus diverged at around 20 mya.
  3. Ancestors of Castor canadensis and Pedetes capanesis diverged from later lineages before 60 mya.
  4. Mus musculus is more closely related to Cricetulus griseus than Nannospalax galili.
  5. All of the following statements are true.

Question 2

At which stage does the somatic cell become “cancerous” and damaging?

A. The oncogenes or tumor-suppressing genes of the somatic cell acquire mutations
B. There is an abnormal proliferation of the somatic cell
C. The abnormally-proliferated somatic cells increase dramatically in size
D. The abnormally-proliferated somatic cells start proliferating to other tissues
E. The abnormally-proliferated somatic cells are detected by the immune system

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question 3

The following statements describe the heterochromatin, except which one?
  1. Heterochromatin are inactive sites of transcription.
  2. Heterochromatin are mostly located at the pericentric and telomeric repeats.
  3. Heterochromatin aggregate mostly near the nuclear envelope in the nucleus.
  4. Heterochromatin appear as lightly stained patches in the chromosome.
  5. Heterochromatin are marked by cytosine methylation.

Question 4

Some RNAs participate in the RNA interference pathway, wherein the RNA is loaded to a protein complex and hybridizes to its target sequence, subsequently leading to the degradation of the target sequence. The following RNAs therefore play a role in the RNA interference, except which one?

Editorial numbering: this is item 4 in sequence; printed label is 3.
  1. piRNA
  2. microRNA
  3. siRNA
  4. shRNA
  5. snoRNA

Question 5

An evolutionary hallmark among placental mammals is the formation of the placenta which allows the embryo to develop inside the female. Remarkably, the synctin protein which enables the placenta formation, is derived from an ancient retrovirus which has been endogenized and became part of the mammalian genome, and are expressed by synctiotrophoblasts. Which is not a property of synctin?

Editorial numbering: this is item 5 in sequence; printed label is 4.

A. Synctin is derived from the envelope protein of an ancient retrovirus.
B. Synctin enables the fusion of synctiotrophoblasts to form a multicellular barrier.
C. Synctin prevents the maternal and fetal blood from physically mixing.
D. Synctin allows the transfer of nutrients, gasses, and wastes between the maternal and fetal blood.
E. All of the above are true.

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question illustration

Question 6

Remdesivir is an antiviral drug used for the treatment of SARS-CoV-2 infection. In which particular aspect of SARS-CoV-2 infection does remdesivir act on?

Editorial numbering: this is item 6 in sequence; printed label is 5.

Question illustration
  1. Remdesivir blocks the binding of the virus to ACE2 receptor.
  2. Remdesivir terminates the viral replication.
  3. Remdesivir prevents the assembly of progeny viruses.
  4. Remdesivir halts the release of progeny viruses
  5. Remdesivir enables the apoptosis of

Question 7

Which of the following is/are a nanomaterial? i. A spherical silver nanoparticle with diameter 10 nm ii. A gold nanorod with length 500 nm and diameter 10 nm iii. A rectangular microcrystal with dimensions 200 nm x 500 nm x 70 nm iv. A 1 μm x 1 μm graphite flake composed of millions of graphene with total thickness 120 nm v. A carbon-based wire with length 1 mm and cross-sectional diameter of 500 nm

A. i only
B. i, ii, and iii
C. i, ii, iii, and iv
D. i, ii, iii, and v
E. i, ii, iii, iv, v

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question 8

Which of the following techniques measures the amount of emitted light?
  1. UV-Vis absorption spectroscopy
  2. NMR spectroscopy
  3. Raman spectroscopy
  4. Fluorescence spectroscopy
  5. Mass spectrometry

Question 9

The structure of Nirmatrelvir, an antiviral drug developed by Pfizer against Covid- 19, is shown below:



How many amino groups are present in this compound?

Question illustration
  1. 0
  2. 2
  3. 4
  4. 5
  5. None of the above

Question 10

Blue dyes were known to be expensive, necessitating extraction of pigments from rare minerals or organisms, so that painters reserved the blue color only for important subjects until the Renaissance. This was the case until 1703, when a Swiss chemist Johann Diesbach discovered how to make the dye Prussian blue, ushering a paintings with lively blue colors such as the Great Wave Off Kanagawa by Hokusai and Starry Night by van Gogh:

Image Credits : Hokusai — Metropolitan Museum of Art, online database : entry 45434, Puiblic domain, https://commons.wikimedia.org/w/index.php?curid=2798407 By Vincent van Gogh - bgEuwDxel93-Pg at Google Arts & Culture, Public Domain, https://commons.wikimedia.org/w/index.php?curid=25498286


An insoluble form of Prussian blue is synthesized from the reaction of a ferric salt and ferrocyanide complex:

2 Fe₂(SO₄)₃ (aq) + 3 K₄Fe(CN)₆ (aq) ⟶ Fe₄[Fe(CN)₆]₃ (s) + 6 K₂SO₄ (aq)

In this synthesis reaction, which species is the Lewis acid?


Hint: In this reaction, the potassium cation and sulfate anions may be considered as spectator ions so that the overall reaction is: 4 Fe³⁺ (aq) + 3 [Fe(CN)₆]⁴⁻ (aq) → Fe₄[Fe(CN)₆]₃ (s)

Question illustration

Question illustration
  1. Fe³⁺ cation
  2. Fe²⁺ cation
  3. [Fe(CN)₆]⁴⁻ anion
  4. [SO₄]²⁻ anion
  5. None of the above

Question 11

0.28 g of an unknown gas was found to exert a pressure of 10.5 kPa and occupy a volume of 2.35 L at 25 °C. What is/are the possible identity/ies of the gas? i. carbon monoxide ii. nitrogen monoxide iii. nitrogen gas iv. carbon dioxide v. nitrogen dioxide

Show below is a periodic table for reference:

Question illustration
  1. i only
  2. i and ii
  3. i and iii
  4. i and iv
  5. i, iv, and v

Question 12

The amount of iron in a sample of ore can be determined by dichromate titration: Cr₂O₇²⁻ + Fe²⁺ + H⁺ → Cr³⁺ + Fe³⁺ + H₂O A chemist is analyzing a 1.05 g of a sample of ore. She first added it with concentrated H₂SO₄ until all of the ore had dissolved and added enough water carefully to make a 25 mL solution. After some time, all and then added 0.05 g of Zn granulated zinc metal was added to convert all of the Fe³⁺ ions to Fe²⁺: Fe³⁺ (aq) + e⁻ → Fe²⁺ (aq) In parallel, she prepared the dichromate solution by dissolving 2.04 g of K₂Cr₂O₇ in enough water to make 250. mL stock solution. Using a 10 mL pipet, she transferred exactly 10.00 mL of the unknown solution to an Erlenmeyer flask and added 8 drops of sodium diphenylamine sulfonate indicator. Titration was completed upon addition of 32.5 mL of the dichromate solution. What is the % Fe in the ore sample? Note: Use the following molecular weights: K=39, Cr=52, O=16, Fe=56, H=1 Hint: Dichromate is reduced to chromate with 6 electrons

A. 28.9 %
B. 72.2 %
C. 4.8 %
D. 12.0 %
E. 6.0 %

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question 13

According to the postulates of quantum mechanics, which of the following is NOT a requirement for a wavefunction?
  1. Normalizable
  2. Single-valued
  3. Finite
  4. Analytically Solvable
  5. Continuous

Question 14

Which of the following is NOT true about fluorescence and phosphorescence?

A. Phosphorescence emission lifetimes are generally shorter than fluorescence
B. Fluorescence always involves emission from a single excited state to the singlet ground state
C. Phosphorescence involves emission from a triplet excited state to a singlet ground state
D. Both fluorescence and phosphorescence and luminescence are considered luminescence phenomena
E. None of the above

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question 15

In 2038, humans from planet earth made contact with the living intelligent beings of the cold moon of Saturn, the planet Titan. On this planet, the atmosphere is composed of 1 % methane, which is the source of energy of these beings. These beings therefore developed a temperature scale based on the freezing point (-162 °C) and boiling point (-182 °C) of methane. The freezing point was set to be 0 T while the boiling point was set at 40 T. At this scale, at what would be the absolute zero temperature? (Note: 0 K = -273 °C)

A. −222 T
B. −35.6 T
C. −273 T
D. −89 T
E. −263 T

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question 16

In a 2010 paper published in Nature, Reinabelle Reyes, a Filipino astrophysicist, together with colleagues from the USA and Switzerland, showed that the large-scale distribution of galaxies in the universe is consistent with the prediction of what theory?
  1. Newtonian Mechanics
  2. General Relativity
  3. Special Relativity
  4. Quantum Mechanics
  5. Quantum Chromodynamics

Question 17

A mass of ice at -50 °C is heated slowly until it melts, becomes liquid, and ultimately steam, at 140 °C. Assuming no mass loss during heating, at what stage of the process is the system requiring the most amount of heat?

Assume that the heat capacities of ice, water, and steam are constant in the given temperature ranges: cice=2.108 kJ/kgK, cwater=4.187 kJ/kgK, csteam=1.99 kJ/kgK. Other relevant constants: ΔHfus=334 kJ/kg, ΔHfus=334 kJ/kg, ΔHvap=2260 J/g.
  1. While heating the ice from −50 °C to 0 °C
  2. While the ice melts to water at 0 °C
  3. While water heats from 0 °C to 100 °C
  4. While water vaporizes to steam at 100 °C
  5. While heating steam from 100 °C to 140 °C

Question 18

If you use a flat iron running at 800 W power for 10 minutes in the Philippines where the typical voltage is 210 V, how many electrons would pass through the iron? charge of electron=1.6 × 10⁻¹⁹ C

A. 2.5 × 10²⁰
B. 1.4 × 10²²
C. 1.5 × 10⁻¹⁵
D. 1 × 10²⁸
E. None of the above

Editorial review: explain the scientific issue and state any assumptions needed for a supported answer.

Question 19

What do you call the unusual patch of extremely cold water that emerged in the Arctic in 2011 and helps slow down glacial melting?
  1. Blue Blob
  2. White Blob
  3. Green Spot
  4. Yellow Spot
  5. White Dab

Question 20

By studying the fossils of ancient fish, scientists have speculated that the asteroid that killed most of the dinosaurs hit the earth during which season in the Northern Hemisphere?
  1. Winter
  2. Summer
  3. Autumn
  4. Spring
  5. Ice Age