Chemistry Questions

Q:

Atoms Are Composed Of

A) Electrons and Protons B) Protons and Nuclei
C) Only Electrons D) Electrons and Nuclei
 
Answer & Explanation Answer: D) Electrons and Nuclei

Explanation:

Atoms are composed of Electrons, protons and Neutrons. Protons and Neutrons together called as Nuclei.

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Q:

Order of basicity of amines

Answer

The order of basicity for primary, secondary and tertiary amines are:


Secondary > Primary > Tertiary > NH3


 


* Amines are basic in nature as they have lone pair of electrons on nitrogen. Therefore, they have a strong tendency to donate this lone pair of electrons to electron acceptors.


* The stability of conjugate acids formed is dependent on the extent of H-bonding,and greater the number of H-atoms on N more stable is the conjugate acid.


* The conjugate acid of primary amine is the most stable with greater number (3) of H-bonds than > Secondary > tertiary. But primary amines are less basic than secondary as the electron density on the N atom is less and lone pair of electrons are not readily available for protonation.


* The two opposing factors i.e. the stability of conjugate acids formed and ease of availability of electrons for Protonation, balance each other in case of secondary amines and it is most basic.

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Q:

Which non metal is liquid at room temperature?

A) Mercury B) Caesium
C) Bromine D) Rubidium
 
Answer & Explanation Answer: C) Bromine

Explanation:

Mercury and Bromine both will be in liquid state at room temperature. But mercury is metal. Hence, bromine is the only non metal which is in liquid state at room temperature.

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Q:

Which of the following is a hydrocarbon?

A) C2H6 B) C3H8
C) CH4 D) All of the above
 
Answer & Explanation Answer: D) All of the above

Explanation:

The simplest organic compounds contain only the elements carbon and hydrogen, and are called hydrocarbons.

Here all the given options are hydrocarbons.

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Q:

Which one of the following elements cannot be detected by "Lassaigne's test"?

A) I B) Cl
C) S D) F
 
Answer & Explanation Answer: D) F

Explanation:

The sodium fusion test, or Lassaigne's test, is used in elemental analysis for the qualitative determination of the presence of foreign elements, namely halogens, nitrogen, and sulphur, in an organic compound. It was developed by J. L. Lassaigne.Silver fluoride is soluble in water and does not precipitate and thus this method cannot be used for detection of fluorine.

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Q:

Nucleic acids are polymers of

A) Nucleotides B) Aminoacids
C) Proteins D) Sugars
 
Answer & Explanation Answer: A) Nucleotides

Explanation:

Nucleic acids are polymers of individual nucleotide monomers.

Each nucleotide is composed of three parts:

a 5-carbon sugar,

a phosphate group, and

a nitrogenous base.

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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:

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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