Class 9 Chemistry - MCQ Test (27-01-2017) - Class 9 MCQ

Atomic number (Z) is defined as the number of protons present in the nucleus of an atom.

Isotopes are atoms with the same number of protons but different number of neutrons. Since the atomic number is equal to the number of protons and the atomic mass is the sum of the number of protons and neutrons, it can also be said that isotopes are atoms of the same element with the same atomic number but different mass number. They have the same chemical properties.

Molecular mass of Sodium is 23 u. So, 23 g of Sodium (Na) is equal to 1 mole of Na.
Number of moles of Na present in 2.3 g of Na = Given mass of Na / Molar mass of Na = 2.3 / 23 = 0.1 mole

Both the statements are correct. A mole is also known as a chemist's dozen. A mole, just like a dozen, is a common counting unit. A counting unit is a convenient number that makes it easier to count objects. The mass of one-twelfth of the mass of one atom of Carbon is taken as 1 u.

Desert cooler causes cooling effect due to evaporation of water as evaporation causes cooling effect. A desert cooler works more effectively when weather is hot and dry.

The rate of evaporation increases with increase in temperature, surface area & wind speed but decrease by the increase in humidity.

Electronic configuration of element X (Atomic number 16) is 2, 8, 6 and that of element Y (Atomic number 16) is 2, 8, 7. Element Y requires only one electron to complete the octet but X requires 2 electrons. So, Y will be more reactive.

Helium (He) has two electrons in its atom. The cation (He²⁺) is formed through the loss of 2 electrons from the outer-most shell of the atom. Hence, the number of electrons in He²⁺ will be 0

Fixed number of atoms or molecules present in gram atomic mass of an atom or molecules is 6.022 × 10²³.This number is known as Avogadro constant.

Number of moles in 60 g of Calcium = Given mass of Calcium / Atomic mass of Calcium = 60/40 = 1.5 mol

By touching the surface of china dish. This is due to the fact that to change from liquid to the vapour state, alcohol requires latent heat of vaporisation. the alcohol takes this heat of vaporisation from china dish. The china dish loses heat and gets cooled.

Electronic configuration of Carbon (C) is 2, 4. The first shell contains 2 electrons and second shell contains 4 electrons. Hence, the number of electrons in its second shell is twice the number of electrons in its first shell.

An anion is formed by gaining electron(s) from other atoms. Hence, an anion contains more electrons than protons. On the other hand, a cation is formed through the loss of electron(s). A neutral atom will have the same number of negatively-charged electrons as well as positively-charged protons.

Molecular mass of H₂O₂ is 34 u. So, 34 g of hydrogen peroxide will contain 1 moles. Therefore, 17 g of hydrogen peroxide will contain 17/34 moles or 1/2 mole.

H₂SO₄ is composed of 2 Hydrogen, 1 Sulphur and 4 Oxygen atoms. It relative molecular mass is 98.

Evaporation of ether occurs due to absorption of heat by surrounding. So, it is an endothermic process.The chemical reaction in which heat is absorbed in called as an endothermic reaction. The reaction in which heat is evolved is called exothermic reaction and the reaction in which no thermal changes occur is called athermic process.

Air is a mixture of gases. Two main constituents of air is  Nitrogen (78%) and Oxygen (21%). Other gases include carbon dioxide, helium, water vapour etc.

Chlorine is found naturally in two isotopic forms having atomic mass of 35 u and 37 u. The two isotopic forms occur in the ratio of 3:1. That makes the average atomic mass of chlorine 35.5 u

The nature of cathode rays does not depend on the nature of gas taken in the cathode tube. Cathode rays travel in straight path and have energy that can rotate a light paddle wheel placed in their path.

Number of moles present in 2 g of Sulphur = 2/32 = 0.0625 moles. Atomic mass of Calcium is 40 u. Mass of Calcium containing 0.0625 moles of atoms = 0.0625×40=8g.

Dalton was the first to state that the smallest indivisible portion of matter is an atom.
The law of conservation of mass was given by A.Lavoisier. The law of constant proportions was stated by Louis Proust. The molecules of noble gas elements are monoatomic in nature.

Naphthalene, camphor, iodine and ammonium chloride are sublime substance. So, statement B is correct. Petrol, ether, acetone and carbon tetrachloride are volatile liquid but water is not a volatile liquid.

The cloth soaked in water takes longer time in drying as it is less volatile. Cloth soaked in alcohol is will take less time than water and cloth soaked in ether will dry quickly as it is highly volatile. So, correct order is Water < Alcohol < Ether.

An isotope of Uranium is used in nuclear reactor. Isotope of cobalt is used in treatment of cancer and an isotope of carbon is used for carbon-dating technique. Isotope of iodine is not used in cancer treatment.

Valency is the combining capacity of an element. If an element has 8 valency then it's outer most shell has 8 electrons or noble gas configuration.

4 g of methane will contain 4/16 moles of molecules = 0.25 moles
​11 g of CO₂ will contain 11/44 moles = 0.25 moles. Hence, both will contain an equal number of moles and an equal number of molecules.

Positive (+ve) ions migrate towards (negatively charged) cathode on passing electric current.

The process of changing solid directly into gases without changing into liquid is called sublimation.sugar, urea and ice are not sublime substance, only Iodine is a sublime substance.

Sulphur dioxide gas is collected in the lab in a gas jar by upward displacement of the air because Sulphur dioxide gas is heavier than air. The gases lighter than air are collected by downward displacement of water.