FREE EJU Science Questions and Answers

Question 1

The water of 100 g at 10 °C is placed in a container that has a heat capacity of 150 J/K and is at temperature t. After sufficient time elapses, the container's temperature changes to 0.0 °C. Also, a portion of the water in the container turns into ice, with the container now holding ice of 5.0 g at 0.0 °C and water of 95 g at 0.0 °C. The specific heat of water is 4.2 J/(g ‥ K), and the heat of fusion of ice is 330 J/g. Assume that there is no exchange of heat with the environment.

What is t (in °C)?

Accepted Answer

-39

Answer

-54

Answer

-43

Answer

-21

Answer

-17

Answer

-4.0

Question 2

The following reaction is in an equilibrium state. Among the following statements about this reaction, two are correct. Choose the correct combination.

(a) If the temperature of this reaction is raised, the equilibrium constant will become smaller.
(b) If a catalyst is added, the equilibrium constant will become larger since the rate of reaction increases.
(c) Though the path of the reaction will not change by adding a catalyst, the activation energy of the reaction will become smaller.
(d) It is impossible to derive an equation explaining the relation between the rate of reaction and the concentration of reactants directly from the chemical equation.

Accepted Answer

a, d

Answer

a, b

Answer

a, c

Answer

b, c

Answer

b, d

Answer

c, d

Question 3

Among the gases generated by means of the following procedures (a)-(d), two exhibit reducing ability. Choose the correct combination.

(a) Aqueous sodium hydroxide (NaOH) is added to aluminum (Al).
(b) Concentrated sulfuric acid (H≥SO4) is added to sodium chloride (NaCl) and the mixture is heated.
(c) Concentrated hydrochloric acid (HCI) is added to manganese(IV) oxide and the mixture is heated.
(d) Dilute sulfuric acid (H2SO4) is added to iron(II) sulfide (FeS).

Accepted Answer

a, d

Answer

a, b

Answer

a, c

Answer

b, c

Answer

b, d

Answer

c, d

Question 4

From the choices below, choose the statement that correctly describes ribosomes:

Accepted Answer

Ribosomes are the site of protein synthesis.

Answer

Prokaryotic ribosomes reside in the cytoplasm; eukaryotic ribosomes reside in the nucleus.

Answer

Ribosomes have a double-membrane structure.

Answer

Ribosomes contain an enzyme that breaks down excess proteins.

Question 5

The statements below describe protein structure. Choose the combination indicating the two statements that are correct:

(a) There are 20 types of amino acids that are used to form proteins.
(b) A sequence of amino acids that are linked together is described as the primary structure; the bonds joining these amino acids together are called S-S bonds (disulfide bonds).
(c) Some proteins are made up of multiple polypeptide chains aggregated together.
(d) The a-helix and B-sheet structures are described as tertiary structures.

Accepted Answer

a, с

Answer

a, b

Answer

a, d

Answer

b, c

Answer

b, d

Answer

c, d

Question 6

From the choices below, choose the statement that correctly describes photosynthesis in green sulfur bacteria:

Accepted Answer

A photosynthetic pigment called bacteriochlorophyll is used in photosynthesis in green sulfur bacteria.

Answer

Photosynthesis in green sulfur bacteria takes place in the chloroplasts.

Answer

Oxygen is released in the process of photosynthesis in green sulfur bacteria.

Answer

Electrons from H2O are used to synthesize organic compounds in the process of photosynthesis in green sulfur bacteria.

Question 7

What happens in the human body when the body temperature decreases? From the choices below, choose the statement that is NOT correct.

Accepted Answer

Metabolism in the liver and skeletal muscles is inhibited.

Answer

Heartbeat is accelerated by the action of the sympathetic nervous system.

Answer

Adrenaline secretion is stimulated.

Answer

Arrector pili muscles contract.

Answer

Blood vessels in the skin constrict.

Question 8

From the choices below, choose the statement that correctly describes a human reflex.

Accepted Answer

The pathway by which excitation is transmitted during a reflex is called the reflex arc.

Answer

The center of the patellar tendon reflex is the medulla oblongata.

Answer

The center of the flexor reflex is the midbrain.

Answer

During a reflex, the excitation is transmitted to the reflex center via the cerebrum.

Question 9

The substances listed below are believed to have been in existence or formed during the process of chemical evolution that preceded the emergence of life. From the choices below, choose the answer that correctly arranges a - c in the order in which they appeared.

(a) Proteins, nucleic acids, etc.
(b) Amino acids, sugars, phospholipids, etc.
(c) Hydrogen sulfide, hydrogen, ammonia, methane, etc.

Accepted Answer

c → b → a

Answer

a → b → c

Answer

a → c → b

Answer

b → a → c

Answer

b → c → a

Answer

c → a → b

Question 10

Innate behaviors and learned behaviors are two categories of animal behavior. From the choices below, choose the answer that best represents an example of learned behaviors.

Accepted Answer

The sea hare retracts its gill when a tactile stimulus is applied to its siphon. However, when the stimulus is applied repeatedly, the sea hare stops retracting its gill.

Answer

Humans reflexively draw back their hands when their fingers touch something hot.

Answer

During breeding season, male three-spined sticklebacks (a freshwater fish) attack other red-bellied males that enter their territory, but do not attack females whose abdomen is swollen with eggs.

Answer

Male silkmoths are attracted by a pheromone to locate females.

Answer

As exemplified by how earthworms move away from light, some animals move in a certain direction in response to a specific stimulus, such as light or a chemical substance.