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

Explanation:
Given:
*Water: 100 g at 10°C
*Container heat capacity: 150 J/K
*Ice formed: 5 g
*Specific heat of water: 4.2 J/(g·K)
*Heat of fusion of ice: 330 J/g

Steps:
1. Heat lost by water cooling to 0°C: 100 × 4.2 × 10 = 4200J
2. Heat to freeze 5 g of water: 5 × 330 = 1650J
3. Total heat lost: 4200 + 1650 = 5850J
4. Heat gained by container: 150 × (0 − t) = −150t
5. Solve for 𝑡:
−150t = 5850
t = −39

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

Explanation:
(a) If the temperature of this reaction is raised, the equilibrium constant will become smaller.
- This is correct for exothermic reactions. Increasing temperature shifts the equilibrium to favor the reactants, decreasing the equilibrium constant.

(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.
- This is correct. The rate law is determined experimentally and cannot be derived directly from the stoichiometric coefficients of the chemical equation.

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

Explanation:
(a) Aqueous sodium hydroxide (NaOH) is added to aluminum (Al).
- This reaction produces hydrogen gas

(d) Dilute sulfuric acid is added to iron (II) sulfide (FeS).
- This reaction produces hydrogen sulfide gas

Question 4

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

Accepted Answer

Ribosomes are the site of protein synthesis.

Answer

Explanation:
Ribosomes are responsible for translating mRNA into proteins, making them essential for protein synthesis in both prokaryotic and eukaryotic cells.

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

Explanation:
(a) There are 20 types of amino acids that are used to form proteins. - This statement is correct. Proteins are composed of 20 different amino acids, each with unique chemical properties that contribute to protein structure and function.

(c) Some proteins are made up of multiple polypeptide chains aggregated together. - This statement is also correct. Proteins can have a quaternary structure, which involves multiple polypeptide chains coming together to form a functional protein complex.

EJU - Examination for Japanese University Practice Test

EJU - Examination for Japanese University Practice Test

FREE EJU Science Questions and Answers