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:

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:

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:

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:

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:

Cutting and peeling of onion brings tears to the eyes because of the presence of _____ ?

A) Amino acid	B) Sulfur
C) Carbon	D) Fat

Answer & Explanation Answer: B) Sulfur

Explanation:

Cutting and Peeling of onion brings Tears to the eyes because of presence of Sulphur in the cell.

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Q:

When combining with nonmetallic atoms, metallic atoms generally will

A) Lose electrons and forms cations	B) Gain electrons and forms anions
C) Lose electrons and forms anions	D) Gain electrons and forms cations

Answer & Explanation Answer: A) Lose electrons and forms cations

Explanation:

When combining with nonmetallic atoms, metallic atoms generally will Lose electrons and forms cations.

As the ionization energy of te metals are very low, so they can easily lose electrons and form positively charged ion called cations.

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