Some Basic Concepts of Chemistry Test

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Some Basic Concepts of Chemistry Test - 34

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Weekly Quiz Competition

Question 1
1 / -0

16.8 g of metal carbonate on thermal decomposition gave 8 g of metallic oxide and 8.8 g of carbon dioxide. They follow:

A
Law of constant proportion

B
Law of multiple proportion

C
Law of conservation of mass

D
None of the above

Solution

$Metal\ carbonate\ (16.8\ g) \rightarrow Metallic\ oxide\ (8\ g) + Carbon\ dioxide\ (8.8\ g)$

The total mass of reactants (metal carbonate) is 16.8 g.
The total mass of products (metallic oxide + carbon dioxide) is 8 + 8.8 = 16 g.

Since the total mass of reactants and products remains the same, this reaction follows the law of conservation of mass.
Question 2
1 / -0

Given:
Mass of beaker is X g
Mass of beaker + mixture is Y g
Mass of washed and dried sand is Z g
Find the percentage of sand in the mixture.

A
$\frac{Y-X}{100}\times Z$

B
$\frac{Y-X}{Z}\times 100$

C
$\frac{Z}{Y-X}\times 100$

D
$\frac{100}{Y-X}\times Z$

Solution

Mass of mixture= $Y-X$
Percentage of sand= $\frac{weight of sand}{weight of mixture}\times 100$
= $\frac{Z}{Y-X}\times100$
Question 3
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$AgNO_3+NaCl\rightarrow AgCl+NaNO_3$ . In this reaction, mass of $AgNO_3$ and $NaCl$ is equal to the mass of $AgCl$ and $NaNO_3$ . Then this chemical reaction satisfies:

A
Law of constant composition

B
Law of conservation of mass

C
Gay Lussac's law

D
Law of multiple proportion

Solution

Law of conservation of mass states that "In a chemical reaction, mass of the products will always be equal to the mass of the reactants".
Question 4
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During any chemical change, the total mass of the products is equal to the total mass of reactants. This is a statement according to:

A
Law of conservation of mass

B
Law of constant composition

C
Law of multiple proportion

D
Law of reciprocal proportion

Solution

According to the law of conservation of mass, the mass of products in a reaction must be equal to the mass of reactants, which can be stated as "mass is neither created nor destroyed during a chemical reaction".
Question 5
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What is a chemical reaction?

A
Reaction that is always endergonic.

B
Rearrangement of electrons in a chemical bond.

C
Both $A$ and $B$ .

D
None of the above.

Solution

A chemical reaction is the transformation of the chemical composition of one substance into other in which electron rearrangement takes place.

Hence, the correct option is $B$
Question 6
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When magnesium is burnt in air, the weight of magnesium :

A
increases

B
decreases

C
remains same

D
Depends on the atmosphere

Solution

When magnesium is burnt in air, the weight of magnesium increases due to the formation of $MgO$ .

$2Mg+O_2\rightarrow 2MgO$
Question 7
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The current model of atomic structure is the:

A
Quantum mechanical model

B
Quantum physiochemical model

C
Atomic mass theory

D
None of the above

Solution

The model that is used and accepted scientists these days, is made by Schrödinger.

Schrödinger used mathematical equations to describe the likelihood of finding an electron in a certain position. This atomic model is known as the quantum mechanical model of the atom.

Quantum mechanics is based on Schrödinger’s wave equation and its solution. The solution of the wave equation brings the idea of shells, sub-shells and orbitals.

Hence, option A is correct.
Question 8
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$2Pb(NO_3)_2\rightarrow 2PbO+X+O_2$

What is $'X'$ in the given balanced chemical equation?

A
$4NO$

B
$4NO_2$

C
$2PbNO_2$

D
$N_2O_5$

Solution

Chemical equation is given by:

$2Pb(NO_3)_2 (s) \xrightarrow{\Delta} 2PbO (s) + 4NO_2 (g) + O_2 (g)$

When heated, lead(II) nitrate crystals decompose to lead(II) oxide, oxygen and we can see brown fumes of nitrogen dioxide.
Question 9
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Magnesium + Oxygen $\longrightarrow$ Magnesium Oxide + Oxygen
48.6 g + 50.0 g $\longrightarrow$ 80.6 g + ?

Predict the mass of oxygen that will be left over after the reaction of 48.6 grams of magnesium with 50.0 grams of oxygen.

A
20.6

B
19.6

C
18

D
17.6

Solution

According to law of conservation of mass, the total mass of reactants must equal the total mass of products
If we assume the mass of oxygen as $X$ g then,

Total mass of reactants = Total mass of products

$48.6+50=80.6+X$

$X = 18\ g$
Question 10
1 / -0

The chemical equation is balanced to satisfy one of the following laws in chemical reactions. This law is known as the:

A
law of conservation of mass.

B
law of multiple proportions

C
law of chemical equilibrium.

D
none of these

Solution

Basically, the chemical equations are the symbolic representations of chemical reactions in which the reactants and products are expressed in terms of their respective chemical formulae. These equations satisfy the law that matter can be changed from one form into another but the total amount of mass remains constant. According to the law of conservation of mass, the mass of products in a reaction must be equal to the mass of reactants so the balancing of equations is done to obey this law.

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Re-Attempt Weekly Quiz Competition

Some Basic Concepts of Chemistry Test - 34

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Some Basic Concepts of Chemistry Test - 34

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Question 1

Law of constant proportion

Law of multiple proportion

Law of conservation of mass

None of the above

Solution

Question 2

Y−X100×Z\frac{Y-X}{100}\times Z100Y−X​×Z

Y−XZ×100\frac{Y-X}{Z}\times 100ZY−X​×100

ZY−X×100\frac{Z}{Y-X}\times 100Y−XZ​×100

100Y−X×Z\frac{100}{Y-X}\times ZY−X100​×Z

Solution

Question 3

Law of constant composition

Law of conservation of mass

Gay Lussac's law

Law of multiple proportion

Solution

Question 4

Law of conservation of mass

Law of constant composition

Law of multiple proportion

Law of reciprocal proportion

Solution

Question 5

Reaction that is always endergonic.

Rearrangement of electrons in a chemical bond.

Both AAA and BBB.

None of the above.

Solution

Question 6

increases

decreases

remains same

Depends on the atmosphere

Solution

Question 7

Quantum mechanical model

Quantum physiochemical model

Atomic mass theory

None of the above

Solution

Question 8

4NO4NO4NO

4NO24NO_24NO2​

2PbNO22PbNO_22PbNO2​

N2O5N_2O_5N2​O5​

Solution

Question 9

20.6

19.6

18

17.6

Solution

Question 10

law of conservation of mass.

law of multiple proportions

law of chemical equilibrium.

none of these

Solution

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$\frac{Y-X}{100}\times Z$

$\frac{Y-X}{Z}\times 100$

$\frac{Z}{Y-X}\times 100$

$\frac{100}{Y-X}\times Z$

Both $A$ and $B$ .

$4NO$

$4NO_2$

$2PbNO_2$

$N_2O_5$