1099+ Important Chemistry MCQ Questions Answers

Q:

Which compound contains both ionic and covalent bonds?

A) NaNO3	B) CaSO4
C) NH4Cl	D) All of the above

Answer & Explanation Answer: D) All of the above

Explanation:

Here all the given compounds have both ionic and covalent bonds.

NaNO3 - In Sodium nitrate, Nitrate is covalently bonded as nitrogen is bonded with 3 oxygen atoms. And this nitrate is ionically bonded with sodium.

CaSO4 - In Calcium sulphate, sulphate is covalently bonded as sulphur is bonded with 4 oxygen atoms. And this sulphate is ionically bonded with calcium.

NH4Cl - In Ammonium chloride, ammonium is covalently bonded as nitrogen is bonded with 4 hydrogen atoms. And this ammonium is ionically bonded with chlorine.

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Q:

Curdling of milk is an example of

A) Inversion	B) Denaturation
C) Hydrolysis	D) Coagulation

Answer & Explanation Answer: D) Coagulation

Explanation:

Coagulation :: The action or process of a liquid, especially blood, changing to a solid or semi-solid state.

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Q:

What is the gram formula mass of ${Li}_{2} {SO}_{4}$ ?

A) 101.2487	B) 109.9446
C) 111.2687	D) 106.5871

Answer & Explanation Answer: B) 109.9446

Explanation:

The term gram formula mass is synonymous with molecular mass. So, to get this, we must add molar mass of all the elements in this compound.

Given compound is Lithium Sulphate - ${Li}_{2} {SO}_{4}$

Elemental calculation ::

Li - Lithium - 6.941 - 2 - 13.88200 %
S - Sulfur - 32.065 - 1 - 32.065 %
O - Oxygen - 15.9994 - 4 - 63.9976 %

Now, total = 12.6264 + 29.1647 + 58.2090 = 109.9446

Hence, the gram formula mass of Li2SO4 = 109.9446.

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Q:

Permanent hardness of water is due to the presence of ?

A) Calcium sulphate	B) Calcium bicarbonate
C) Sodium bicarbonate	D) Magnesium bicarbonate

Answer & Explanation Answer: A) Calcium sulphate

Explanation:

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Q:

Which element has similar properties to Beryllium?

A) Manganese	B) Calcium
C) Both A & B	D) Helium

Answer & Explanation Answer: B) Calcium

Explanation:

The elements in the same column will have similar properties. Beryllium is the group II element. Group II elements are magnesium, calcium, strontium, barium and radium. Hence, these show the similar prperties.

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Q:

Modern periodic table is based on atomic number of the elements. The significance of atomic number was proved by the experiment of ________

A) Moseley's work on X-ray spectra	B) Bragg's work on X-ray diffraction
C) Mulliken's oil drop experiment	D) Discovery of X-ray by Roentgen

Answer & Explanation Answer: A) Moseley's work on X-ray spectra

Explanation:

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Q:

The degree of dissociation ( $α$ ) of a weak electrolyte, $A_{x} B_{y}$ is related to van't Hoff factor (i) by the expression:

$1 . α = \frac{x + y + 1}{i - 1}$

$2 . α = \frac{x + y - 1}{i - 1}$

$3 . α = \frac{i - 1}{x + y + 1}$

$4 . α = \frac{i - 1}{x + y - 1}$

A) 1 is correct	B) 2 is correct
C) 3 is correct	D) 4 is correct

Answer & Explanation Answer: D) 4 is correct

Explanation:

Van't Hoff factor (i) = $\frac{O b s e r v e d C o l l i g a t i v e P r o p e r t y}{N o r m a l C o l l i g a t i v e P r o p e r t y}$

$\begin{matrix} A_{x} B_{y} \\ 1 - α \end{matrix} \to \begin{matrix} x A^{+ y} \\ x α \end{matrix} + \begin{matrix} y B^{- x} \\ y α \end{matrix}$

Total Moles = $1 - α + x α + y α$ = $1 - α (x + y - 1)$

$i = \frac{1 + α (x + y - 1)}{1}$

$\Rightarrow α = \frac{i - 1}{x + y - 1}$

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Q:

Water is an example of?

A) Element	B) Molecule
C) Compound	D) Both B & C

Answer & Explanation Answer: D) Both B & C

Explanation:

Why Water Is Not an Element :

An element is a substance consisting of only one type of atom. Water consists of two types of atoms: hydrogen and oxygen.

water is both a molecule and a compound :

A compound forms whenever two or more atoms form chemical bonds with each other. The chemical formula for water is H2O, which means each molecule of water consists of one oxygen atom chemically bonded to two hydrogen atoms.

Thus, water is a compound.

It's also a molecule, which is any chemical species formed by two or more atoms chemically bonded to each other. The terms molecule and compound mean the same thing and can be used interchangeably.

Hence, water is both a molecule and a compound.

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