Chemistry Questions

Q:

Alcohol is a stimulant. true or false

A) TRUE B) FALSE
Answer & Explanation Answer: B) FALSE

Explanation:

Alcohol is a drug.

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Q:

Which scientist established the Law of Octaves?

A) John Newlands B) Antoine Lavoisier
C) Alfred Nobel D) Marie Curie
 
Answer & Explanation Answer: A) John Newlands

Explanation:

Law of Octaves states that "If the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements." That is every 8th element have the same physical and chemical properties. This was established by the British scientist John Newlands in the year 1865.

Which_scientist_established_the_Law_of_Octaves1559374791.jpg image

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Q:

Another name for the activated complex is

A) Transmission state B) Energy barrier
C) Collision group D) Transition state
 
Answer & Explanation Answer: D) Transition state

Explanation:

The minimum amount of energy required for a particular reactants to convert into products and is called as Activation Energy.

 

Another_name_for_the_activated_complex_is1559538681.jpg image

 

This activation complex is also termed as Transition State because according to Transition State Theory at transition state the existing bonds tend to increase in length and become weaken while, the new forming bonds tend to decrease in length and start becoming stronger.

Hence, the activated complex is in transition between reactants and products.

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Q:

Lime is sometimes applied to soil in order to

A) increase the acidity of the soil B) make the soil more porous
C) restore nitrates to the soil D) increase the alkalinity of the soil
 
Answer & Explanation Answer: D) increase the alkalinity of the soil

Explanation:

Lime is sometimes applied to soil in order to increase the acidity of the soil.

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Q:

Which is a characteristic of a Mixture?

A) a pure substance B) chemically comined
C) they can be mixed in some fixed ratio D) it is either homogenous or heterogenous
 
Answer & Explanation Answer: D) it is either homogenous or heterogenous

Explanation:

A mixture is the blending of two or more dissimilar substances.

 

Characteristics of a Mixture:

1. It has No formula.

2. It is an impure sustance

3. They can be mixed in any ratio.

4. The properties of the mixture are the properties of its constituents.

5. Constituents can e easily seperated by physical methods.
eg: Heating, Drying, Crystallization, Distillation etc...

6. It is either homogenous or heterogenous.

 

A major characteristic of mixtures is that the materials do not chemically combine. Mixtures can be divided into those that are evenly distributed (homogeneous) and those that aren't (heterogeneous).

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Q:

Which of the following mixtures is not a colloid?

A) Sugar water B) Milk
C) Paint D) Fog
 
Answer & Explanation Answer: A) Sugar water

Explanation:

Colloids include gels, sols, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.

These Colloid substances consists of ultramicroscopic particles of one substance dispersed through another substance from which we cannot separate them.

 

Sugar water is not a colloid and it is a solution in which we can separate them.

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Q:

Which three components are common to all amino acids?

Answer

Any two amino acids vary structure by the r-group, otherwise all amino acids are in the same structure. All amino acids have in common carboxyl group -COO , amino group -NH3+ and a hydrogen -H and a r-group which are all bonded to a central carbon.

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Q:

Which of the following reactions are redox reactions?

A) Ba(s)+Cl2(g)--->BaCl2(s) B) Mg(s)+Br2(l)--->MgBr2(s)
C) Al(s)+3Ag^+(aq)--->Al^3+(aq)+3Ag(s) D) All of the above
 
Answer & Explanation Answer: D) All of the above

Explanation:

A redox reaction is a type of reaction which involves transfer of electrons among two species. This reaction is also called oxidation-reduction reaction.

In oxidation process, there is an increase in oxidation state of an atom, ion or molecule by losing the electrons.

In reduction process, there is a decrease in oxidation state of an atom, ion or molecule by accepting the electrons.

1)

image

In this reaction, Ba undergoes oxidation and Cl undergoes reduction.
This reaction is redox reaction.
In this reaction, oxidation number of Ba increases from 0 to +2 . So, Ba undergoes oxidation. The oxidation number of Cl decreases from 0 to -1. So, Cl undergoes reduction.

 

2) 

 

image

From this above reaction, it is clear that Aluminum undergoes oxidation and silver undergoes reduction.
Due to this, this reaction is redox reaction.

In this reaction, oxidation number of Aluminum increases from 0 to +1. So, aluminum undergoes oxidation. The oxidation number of silver decreases from +1 to 0. So, silver undergoes reduction.

 

3)


image

In this reaction, Mg undergoes oxidation and Br undergoes reduction.
This reaction is redox reaction.
The reactions 1, 3 and 4 are redox reactions.
In this reaction, oxidation number of Mg increases from 0 to +2 . So, Mg undergoes oxidation. The oxidation number of Br decreases from 0 to -1 . So, Br undergoes reduction.

 

Hence all the above reactions are redox reactions.

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