Chemistry Questions

Q:

What is the conjugate base of H2O?

A) NH3+ B) OH-
C) H2O D) All the above
 
Answer & Explanation Answer: B) OH-

Explanation:

A conjugate acid, is a species formed by the reception of a proton (H+) by a base—in other words, it is a base with a hydrogen ion added to it.

On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid.

Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic.

Represented as the following chemical reaction:

Acid + Base ⇌ Conjugate Base + Conjugate Acid

 

The water molecule is the conjugate acid of the hydroxide ion after the latter received the hydrogen proton donated by ammonium. On the other hand, ammonia is the conjugate base for the acid ammonium after ammonium has donated a hydrogen ion towards the production of the water molecule. We can also refer to OH- as a conjugate base of H2O, since the water molecule donates a proton towards the production of NH+4 in the reverse reaction, which is the predominating process in nature due to the strength of the base NH3 over the hydroxide ion.

 

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4 9437
Q:

Which acid is produced when milk gets sour?

A) Lactic acid B) Acetic acid
C) Tartaric acid D) Butyric acid
 
Answer & Explanation Answer: A) Lactic acid

Explanation:
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11 9412
Q:

The freezing point of water at 760mm pressure is

A) 0 K B) 273 K
C) 273 C D) -273 C
 
Answer & Explanation Answer: B) 273 K

Explanation:

K is degree kelvin

Zero K corresponds to -273  K = C + 273

The freezing point of water being 0 C, on the kelvin scale it is 0 C + 273 K

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12 9407
Q:

Apart from proposing atomic theory, what did John Dalton researched on?

 

A) Plants B) Colour blindness
C) Penicillin D) Plastic
 
Answer & Explanation Answer: B) Colour blindness

Explanation:
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2 9385
Q:

A gas absorbs a photon of 355 nm and emits at two wavelengths. If one of the emissions is at 680 nm, the other is at :

A) 518 nm B) 1035 nm
C) 325 nm D) 743 nm
 
Answer & Explanation Answer: D) 743 nm

Explanation:

1λ=1λ1+1λ2

1355=1680+1λ2

1λ2=680-355680×355

λ2=743nm.

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Q:

The law of constant proportions was enunciated by

A) Dalton B) Berthelot
C) Avogadro D) Proust
 
Answer & Explanation Answer: D) Proust

Explanation:
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16 9258
Q:

An element which is preserved under water is 

A) sodium B) sulphur
C) red phosphorus D) white phosphorus
 
Answer & Explanation Answer: D) white phosphorus

Explanation:

White phosphorus undergoes spontaneous combustion when exposed to air. In order to prevent this spontaneous ignition, it is preserved under water. 

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27 9245
Q:

The formula C6H14 represents the hydrocarbon ___.

 

A) Hexene B) Heptyne
C) Hexane D) Hexyne
 
Answer & Explanation Answer: C) Hexane

Explanation:
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