Tag: chemistry

Questions Related to chemistry

Which is the most active element among folllowing?

chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

  1. Chlorine

  2. Oxygen

  3. Sulfur

  4. Fluorine

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Correct Option: D
Explanation:

Most active element is Fluorine. The reduction potential of fluorine is very high. Hence, it is extremely reactive in nature. Also F-F bond energy is low (38 kcal/mol). The valence shell electron configuration of fluorine $2s^22p^5$  indicates that it has very strong tendency to take up one electron to attain stable noble gas configuration. Hence, it has high reactivity.

Which of the following is correct?

chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

  1. Iodine is solid

  2. Chlorine is insoluble in water.

  3. Iodine is more reactive than bromine.

  4. Bromine is more reactive than chlorine.

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Correct Option: A
Explanation:

The reason is that the attractive forces between the molecules of these elements increase from top to bottom of the Group.

In iodine, the electrons are so far from the nuclei that the electron clouds can easily distort. The London dispersion forces are strong. So the Iodine is solid.

Hence option A is correct.

Formula of Freon is:

chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

  1. $CCl _2F _2$

  2. $COCl _2$

  3. $SO _2Cl _2$

  4. none of these

Show answer
Correct Option: A
Explanation:

$CCl _2F _2$ is called as freons or chloro floro carbons.

Hence option A is correct.

Have you ever noticed the fact that two siblings can have different personalities? Even though two people may be members of the same family, it does mean that they will behave in similar ways.
The same thing can be said about elements in a group ("family") on the periodic table. For example, fluorine and iodine are members of the halogen family, but their physical properties are different, as shown in the table below.

Element Melting Point $(^{\circ}C)$ Boiling Point $(^{\circ}C)$
Fluorine $-220$ $-188$
Iodine $+118$ $+184$

Which of the following is the BEST explanation for these differences in melting and boiling point?

chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

  1. Fluorine has a higher value for electronegativity than iodine.

  2. The covalent bond in the fluorine molecule is stronger than the covalent bond in the iodine molecule.

  3. Iodine molecules are larger and more polarizable than fluorine molecules.

  4. Fluorine is a nonpolar molecule, but iodine is a polar molecule.

Show answer
Correct Option: C
Explanation:

As we move down the group of halogens the size of elements increases thereby increasing the Van der Waal forces; hence boiling and melting point of Iodine is more than Fluorine molecule.

Which is soluble in water :

chemistry p- block elements-ii group 17 elements - general properties group 17 elements group 17 elements - properties

  1. AgCl

  2. AgBr

  3. AgI

  4. AgF

Show answer
Correct Option: D
Explanation:

Ionic compounds are soluble in water
In AgF  $F^-$ is small onion with high charge density so less polarisation and less covalent character in the whole group of Ag holdies.  AgF is most Ionic in nature.

State whether true or false :

Cutting a log of wood into pieces is a chemical change.

chemistry change around us physical changes changes and their classification physical changes

  1. True

  2. False

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Correct Option: B
Explanation:

Cutting a log to wood into piece does not change the composition of wood hence it is not a chemical change.


It can be defined as physical irreversible change.

Hence the given statement is false.

Changes in which only ____________ properties of a substance change are called physical changes.

chemistry change around us physical changes changes and their classification physical changes

  1. chemical

  2. physical

  3. biological

  4. environmental

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Correct Option: B
Explanation:

Physical properties $-$ Shape, state of the substance size etc.

because these changes does not change the composition of the substance

Pick up the correct statement:

chemistry change around us physical changes changes and their classification physical changes

  1. Boiling points of alkyl halides are greater than those of the corresponding alkanes.

  2. In water, the solubility decreases as $CH _3OH > C _2H _5OH > C _6H _5OH$.

  3. Aniline is a weaker base than ammonia.

  4. All of the above.

Show answer
Correct Option: D
Explanation:

$(A)$  Boiling point $X$ molecular mass of compound hence alkyl halide have greater boiling point

$(B)$  More is the mass of the compound, less is the solubility.
               ${ CH } _{ 3 }OH>{ C } _{ 2 }{ H } _{ 5 }OH>{ C } _{ 6 }{ H } _{ 5 }OH$

$(C)$  Lone pair of aniline in resonance hence a weaker base.

Iron rod turns red on heating. The change is a ___________ .

chemistry physical and chemical changes physical changes changes and their classification physical changes

  1. Physical change

  2. Temperature change

  3. Physical and chemical change

  4. Chemical change

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Correct Option: A

Physical changes are ________.

chemistry change around us physical changes changes and their classification physical changes

  1. Temporary

  2. Permanent

  3. Irreversible

  4. Endothermic

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Correct Option: A
Explanation:

In a physical change, the substances are not altered chemically. No new products are formed. 
A physical change can affect the size, shape or color of a substance but does not affect its composition. The substances may be changed to another phase (i.e. gas, liquid, solid) or separated or combined so physical changes are temporary.

Examples:
when ice melts
when sulfur is mixed with iron filings. 
breaking a glass 
dissolving sugar in water