Atoms and Molecules Test

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Atoms and Molecules Test - 15

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Weekly Quiz Competition

Question 1
1 / -0

Which representation is correct for the compound formed by the combination of calcium and oxygen?

A
CaO

B
OCa

C
CaO₂

D
OCa₂

Solution

While writing the formula of a compound that contains more than one element, the symbol of the more electropositive element is written first, that is, on the left hand side, followed by the less electropositive elements. As calcium is more electropositive than oxygen, it is written on the left hand side. Calcium oxide contains one atom each of calcium and oxygen.

The correct answer is A.

Why alternative B is wrong:

The symbol of calcium oxide cannot be OCa as carbon is more electropositive than oxygen_.

Why alternative C is wrong:

Calcium oxide contains one atom each of calcium and oxygen. Hence, its symbol cannot be CaO₂.

Why alternative D is wrong:

Calcium oxide contains one atom each of calcium and oxygen. Hence, its symbol cannot be OCa₂.

Question 2

1 / -0

Use the following information to answer the next question.

Silver nitrate solution, when treated with NaCl, produces a precipitate of silver chloride. The amount of reactants and products is shown in the reaction given below. The reaction strictly obeys the law of conservation of mass

Ag NO₃ + NaCl → AgCl + NaNO₃

X g 5.85 g 14.35 g 8.5 g

The amount of AgNO₃ (X) used during the reaction is equal to

17.0 g

5.0 g

14.5 g

8 g

Solution

According to the law of conservation of matter, the total mass of the reactants is equal to the total mass of the products.

X + 5.85 g = 14.35 g +8.5 g

X = 17.0 g

The correct answer is A.

Question 3
1 / -0

The chemical formula of carbon dioxide is represented as

A
CO

B
CO₂

C
C₂O

D
C₂O₄

Solution

The formula of the molecule of a compound is indicated by writing the symbols of all elements present in it. It also indicates the number of atoms of each element present in a molecule of that compound. These numbers are written in subscript, next to the symbol of the element. Hence, the chemical formula of carbon dioxide is represented as CO₂.

The correct answer is B.

Why alternative A is wrong:

CO is the chemical formula of carbon monoxide.

Why alternative C is wrong:

The chemical formula of carbon dioxide is represented as CO₂not C₂O.

Why alternative D is wrong:

C₂O₄is the chemical formula of oxalate.
Question 4
1 / -0

According to John Dalton, the tiny particles that constitutes matter are called

A
atoms

B
elements

C
molecules

D
compounds

Solution

John Dalton stated that all matter is made up of tiny particles called atoms. Elements are made up of atoms that are completely identical. Different substances are obtained when atoms of different elements combine chemically.

Hence, the correct answer is option A.
Question 5
1 / -0

Which chemical formula correctly represents the compound that has one nitrogen atom and three hydrogen atoms?

A
NH

B
NH₃

C
N₃H

D
N₃H₃

Solution

The molecular formula of the compound having one nitrogen atom and three hydrogen atoms is NH₃.

The correct answer is B.

Why alternative A is wrong:

NH will be the chemical formula of the compound that contains one nitrogen atom and one hydrogen atom.

Why alternative C is wrong:

N₃H will be the chemical formula of the compound that contains three nitrogen atoms and one hydrogen atom.

Why alternative D is wrong:

N₃H₃ will be the chemical formula of the compound that contains three nitrogen atoms and three hydrogen atoms.

Question 6

1 / -0

Use the following information to answer the next question.

An anion has _____i_____ electrons in its shell than the number of protons in its nuclei, whereas a cation has ______ii_____ protons in its nuclei than the number of electrons in its shell.

The information in which alternative completes the given statement?

i ii

less less

i ii

less more

i ii

more more

i ii

more less

Solution

When an atom or a molecule loses or gains one or more electrons, then this atom or molecule is called an ion. An ion can be positively or negatively charged.

A negatively charged ion is called an anion. It is formed by gaining one or more electrons in its electron shell than the number of protons it has in its nuclei.

A positively charged ion is called a cation. It is formed by losing one or more electrons. Hence, a cation has fewer electrons in its electron shell than the number of protons it has in its nuclei.

The correct answer is D.

Question 7
1 / -0

A polyatomic sulphur molecule has

A
six sulphur atoms.

B
two sulphur atoms.

C
four sulphur atoms.

D
eight sulphur atoms.

Solution

Sulphur does not exist in nature as a single atom. Eight atoms of sulphur combine to form a single molecule of sulphur. The molecular formula of sulphur is represented as S_8.

The correct answer is D.
Question 8
1 / -0

Which chemical formula correctly represents the compound having two hydrogen atoms, one carbon atom, and three oxygen atoms?

A
HCO₃

B
H₂CO₃

C
H₃CO₂

D
H₃C₂O₃

Solution

The molecular formula of the compound having two hydrogen atoms, three oxygen atoms, and one carbon atom is H₂CO₃.

The correct answer is B.

Why alternative A is wrong:

HCO₃ will be the chemical formula of the compound that contains three oxygen atoms, one carbon atom, and one hydrogen atom.

Why alternative C is wrong:

H₃C₂O₃ will be the chemical formula of the compound that contains three hydrogen atoms, two carbon atoms, and three oxygen atoms.

Why alternative D is wrong:

H₃CO₂ will be the chemical formula of the compound that contains three hydrogen atoms, one carbon atom, and two oxygen atoms.

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Re-Attempt Weekly Quiz Competition

Atoms and Molecules Test - 15

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Atoms and Molecules Test - 15

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Question 1

CaO

OCa

CaO2

OCa2

Solution

Question 2

17.0 g

5.0 g

14.5 g

8 g

Solution

Question 3

CO

CO2

C2O

C2O4

Solution

Question 4

atoms

elements

molecules

compounds

Solution

Question 5

NH

NH3

N3H

N3H3

Solution

Question 6

i ii less less

i ii less more

i ii more more

i ii more less

Solution

Question 7

six sulphur atoms.

two sulphur atoms.

four sulphur atoms.

eight sulphur atoms.

Solution

Question 8

HCO3

H2CO3

H3CO2

H3C2O3

Solution

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CaO₂

OCa₂

CO₂

C₂O

C₂O₄

NH₃

N₃H

N₃H₃

i ii

less less

i ii

less more

i ii

more more

i ii

more less

HCO₃

H₂CO₃

H₃CO₂

H₃C₂O₃