Measurements of Matters

Measurements of Matters

 Laws of Chemical Combination

• There are three important laws of chemical combination. :

• i) Law of conservation of mass

• ii) Law of constant proportions

• iii) Law of multiple proportions. 

Multiple Choice

After a chemical reaction, the total mass of reactants and products ______.

• Is always increased

• Is always decreased

• Is not changed

• Is always less or more

Multiple Choice

In the reaction A + B $\rightarrow$ C + D, according to law of conservation of mass, mass of ________.

• A = C

• A + C = E + D

• A + B = C + D

• B = D 

Multiple Choice

The ratio of Hydrogen and Oxygen by mass in water is _______

• 1 : 8

• 8 : 1

• 2 : 1

• 1 : 2

Multiple Choice

A sample of pure carbon dioxide, irrespective of its source contains 27.27% carbon and 72.73% oxygen. The data support _____.

• Law of constant composition

• Law of conservation of mass

• Law of reciprocal proportions

• Law of multiple propotions

Multiple Choice

Two samples of lead oxide were separately reduced to metallic lead by heating in a current of hydrogen. The weight of lead from on oxide was half the weight of lead obtained from the other oxide. The data illustrates _______.

• Law of reciprocal proportions

• Law of constant composition

• Law of multiple proportions

• Law of equivalent proportions

Postulates of Dalton's Atomic theory

• i) All matter is made of very tiny particles called atoms.

• ii) Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction.

• iii) Atoms of a given element are identical in mass and properties.

• iv) Atoms of different elements have different masses & properties.

• v) Atoms combine in the ratio of whole numbers to form compounds.

• vi) The relative number and kinds of atoms are constant in a given compound. 

Multiple Choice

An atom is the smallest unit and is indivisible. This theory was proposed by _______.

• Dalton

• Rutherford

• Thomson

• Bohr

• An element is a pure substance made up of one kind of atoms having the same atomic numbers and which cannot be broken down into two or more substances by any physical or chemical means.

• An atom is the smallest particle of an element that can take part in a chemical reaction.

• An atom consists of sub-atomic particle: electrons, protons and neutrons.

• The protons and neutrons are found in the center or nucleus of the atom collectively called nucleons.

• The Orbits is the imaginary path where electrons revolve around the nucleus of the atom.

• The atomic number of an element is the numbers of protons present in its nucleus. It is denoted by the symbol (Z).

• Thus, the atomic number (Z) = Number of protons in the nucleus= Number of positive charges on the nucleus= Number of electrons around the nucleus in the neutral atom.

• Atomic Mass Number of an element is the total numbers of protons & neutrons present in its nucleus and is denoted by (A).

• Thus, mass number (A) = Number of protons + number of neutrons = Number of nucleons . A= Z + n.

• no. of neutrons [n] = A – Z

Multiple Choice

For ⁵²X₂₄ , number of electrons is _______.

• 52

• 24

• 76

• 28

Multiple Choice

The nucleus of an atom of Phosphorus is represented as ³¹P₁₅. The number of protons, neutrons and electrons in the atom of Phosphorus are respectively _______.

• 15, 31, 15

• 15, 15, 16

• 15, 31, 16

• 15, 16, 15

Multiple Choice

The chemical symbol for sodium is ______.

• So

• Sd

• NA

• Na

Multiple Choice

The symbol of Calcium, Carbon and Copper is ______

• Ca,C,Co

• Ca,C,Cu

• Ca,C,Cr

• CA,C,Cu

Multiple Choice

The correct symbol for silver is ______.

• Ag

• S

• Ar

• AI

Multiple Choice

Plumbum is the Latin name of _______.

• Lead

• Krypton

• Calcium

• Phosphorous

Multiple Choice

The group of symbols of elements based on Latin names out of the following is _______.

• Ca, Ag, Cu

• Ag, Au, K

• Pb, Cl, Cd

• Cs, Fe, Na

Multiple Choice

The chemical symbol for nitrogen gas is _____.

• Ni

• N₂

• N⁺

• N

• The atomic mass unit (amu) is equal to one-twelfth (1/12) of the mass of an atom of carbon-12.

• The atomic mass of an element is a relative quantity and it is the mass of one atom of the element relative to one-twelfth (1/12) of the mass of one carbon-12 atom. 

• The atomic mass of an element expressed in grams is called the Gram Atomic Mass of the element. 

• The relative molecular mass of a substance is the mass of a molecule of the substance as compared to one-twelfth of the mass of one carbon-12 atom

• The molecular mass of a substance expressed in grams is called the Gram Molecular Mass of the substance.

Multiple Choice

The modern atomic weight scale is based on _______.

• C¹²

• O¹⁶

• H¹

• C¹³

Multiple Choice

1 amu is equal to 

• 1/12th of mass of one C –12 

• 1/14th of mass of one C –16 

• 1 g of H2

•  $1.66\times10^{-23}$ kg

Multiple Choice

Molecular mass is defined as the ______.

• Mass of one molecule of any substance compared with the mass of one atom of C – 12

• Mass of one atom compared with the mass of one atom of hydrogen

• Mass of one atom compared with the mass of one molecule

• None of the above

• Electrons in the outermost shell are known as valence electrons.

• The number of electrons, that atom can lose, gain or share during a chemical reaction is called its valency.

• Valency is the combining capacity of an atom or of a radical.

• Certain elements exhibit more than one valency, i.e. they show variable valency. 

Multiple Choice

Which of the following metals does not posses variable valency?

• Copper

• Iron

• Lead

• Sodium

Multiple Choice

Molecular mass of  $Na_2S_2O_3$  is ______ [Na - 23, S - 32, O - 16] 

• 142

• 135

• 158

• 126

Multiple Choice

Co stands for ______ while CO stands for _____.

• the atoms of the element cobalt; carbon monoxide

• the atoms of the element carbon monoxide

• the atom of the element cobalt; the molecules of the compound carbon monoxide

• the molecules and atoms of element carbon

Multiple Choice

To complete the octate, outer most shell of Aluminium _____ .

• Looses two electrons

• Gains three electrons

• Looses three electrons

• Shares four electrons

Multiple Choice

What is the molecular mass of sodium sulphate? [Na-23, S-32, O-16]

• 71

• 119

• 165

• 142

Multiple Choice

Who am I ? My atomic number is 19. ________.

• A solid non-metal of valency 2

• A gas of valency 2

• A metal of valency 1

• A non-metal of valency 4

Multiple Choice

All noble gas molecules are _____.

• Monoatomic

• Diatomic

• Triatomic

• Both I and II

Multiple Choice

Who discovered the law of conservation of mass?

• Dalton

• Lavoisier

• Avogadro

• Bohr

Multiple Choice

A sample of NH₃ molecule irrespective of source contains 82.35% Nitrogen and 17.65% of Hydrogen by mass. This data supports_____.

• Law of Conservation of Mass

• Law of Multiple Proportions

• Law of Definite Proportions

• Avogadro’s Law

Multiple Choice

When 15 g of copper sulphate reacts with 15g of sodium hydroxide, 10 g of copper hydroxide and 20 g of sodium sulphate was formed. The statement depicts the _______.

• law of constant proportions

• law of chemical combinations

• law of conservation of mass

• none of these

Multiple Choice

____ formulated the law of constant proportion.

• Proust

• Newton

• Lavoisier

• Mosley

Multiple Choice

The percentage of copper and oxygen in samples of CuO obtained by different methods were found to be the same. The illustrate the law of _____.

• Constant proportion

• Conservation of mass

• Multiple proportions

• Reciprocal proportions