Tag: chemistry

Questions Related to chemistry

Hydrolysis of urea is an example of

  1. Homogenious reaction

  2. heterogenious reaction

  3. Biomolecular reaction

  4. Both a and b


Correct Option: C
Explanation:

Enzymes are biological catalysts which catalyze the biochemical reactions in living organisms.

Hydrolysis of urea by urease is an example of  biochemical catalysis.

 

Predict block, group and period of $Sb$.

  1. Block-$p$, Period-$5$, Group-$15$

  2. Block-$p$, Period-$5$, Group-$14$

  3. Block-$s$, Period-$5$, Group-$13$

  4. Block-$s$, Period-$5$, Group-$11$


Correct Option: A
Explanation:

Antimony is a chemical element with symbol $Sb$ (from Latin: stibium) and atomic number $51$,group $15$ (pnictogens), $p$-block,period $5$.

Based on modern classification of periodic table atomic number increases on moving from _________ in periodic table.

  1. left to right

  2. right to left

  3. straight

  4. none of these


Correct Option: A
Explanation:

Elements in the same period tend to have shared chemistry and exhibit a  trend in properties with increasing atomic number from left to right.

The modern periodic table is most_________ form of periodic table.

  1. insignificant

  2. Significant

  3. Both A and B

  4. None of these


Correct Option: B
Explanation:

In the standard periodic table, the elements are listed in order of increasing atomic number. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it i.e. it is more significant form of periodic table.

Significance of classification of periodic table is to ___________.

  1. predict the blocks of elements

  2. predicts the groups of elements

  3. both A and B

  4. none of these


Correct Option: C
Explanation:

Periodic classification of elements is the method by which elements are grouped on the basis of their characteristics. Classification of elements in groups provide us a fixed pattern in which the elements change their properties periodically. Periodic table made the study of physical and chemical properties of elements simple and organized.

Classification of periodic table based on atomic number is given by:

  1. Mendeleev's

  2. Mosley

  3. Both A and B

  4. None of these


Correct Option: B
Explanation:

Henry Moseley found a relationship between the X-ray wavelength of an element and its atomic number. Moseley's discovery showed that atomic numbers were in fact based upon experimental measurements.

Alkali and alkaline earth metals are ________ elements.

  1. same

  2. different

  3. both A and B

  4. none of these


Correct Option: B
Explanation:

Alkali and alkaline earth metals are group I and group II elements of s block representative elements with ns$^1$ and ns$^2$ valence shell configuration respectively.


Hence, option B is correct.

Lanthanoids are also called as ___________.

  1. Transition elements

  2. Rare earth elements

  3. Both A and B

  4. None of these


Correct Option: B
Explanation:

Rare earth metals are a group of chemically similar metallic elements comprising the lanthanide series and (usually) scandium and yttrium. They are not especially rare, but they tend to occur together in nature and are difficult to separate from one another.

Alcohols of low molecular weight are:

  1. soluble in water

  2. soluble in water on heating

  3. insoluble in water

  4. insoluble in all solvents.


Correct Option: A
Explanation:

Alcohols of low molecular weight are soluble in water while that of high molecular weight are insoluble in water .because of high hydrogen bonding in low molecular weight Alcinous.

Which of the following statements is not correctly showing the trend of the properties mentioned ?

  1. $CH _3CH _2OH > CH _3CH _2CH _2OH > \underset {(Solubility)}{CH _3CH _2CH _2CH _2OH}$

  2. $CH _3CH _2OH > CH _3CH _2CH _2OH > \underset {(Boiling point)}{CH _3CH _2CH _2CH _2OH}$

  3. $CH _3CH _2CH _2OH > CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH >\underset{Boiling \, point}{CH _3-\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}C}}}-OH}$

  4. $CH _3-{\underset{CH _3}{\underset{|}{\overset{CH _3}{\overset{|}{C}}}}}-OH$<$CH _3{\underset{CH _3}{\underset{|}{CH}}}-CH _2OH$ <$CH _3CH _2CH _CH _2OH$


Correct Option: D
Explanation:
Boiling point and solubility of alcohols is determined by the ease and extent of H-bonding among the alcohol molecules. More is the hydrogen bonding higher is the boiling point and solubility in water. Thus, tertiary alcohols being highly hindered will have least hydrogen bonding and thus low boiling point/solubility as compared to less hindered secondary alcohol.
Therefore the order of boiling point is primary alcohol>secondary alcohol>tertiary alcohol as:
$CH _3CH _2CH _2OH>CH _3CH(CH _3)CH _2OH>CH _3C(CH _3) _2OH$
In case of linear versus branched alcohol, linear alcohol has higher melting/boiling points due to better stacking and surface area contact.
But in case of highly branched vs. branched molecules more sphere-like structure of the molecule better is the stacking thus higher will be the melting point. Thus order of melting point will be
$CH _3CH(CH _3)CH _2OH<CH _3C(CH _3) _2OH<CH _3CH _2CH _2CH _2OH$
A and B. Solubility and boiling point of alcohols depends on the chain length. Longer is the chain length, lesser is the solubility/boiling point as the extent of H-bonding decreases. Also, the hydrophobic nature of the hydrocarbon chain reduces the solubility.
thus order of solubility and boiling point will be:
$CH _3CH _2OH>CH _3CH _2CH _2OH>CH _3CH _2CH _2CH _2OH$