Tag: chemistry

Questions Related to chemistry

Molten NaCl conducts electricity due to the presence of :

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. free molecules

  2. free ions

  3. free electrons

  4. free atoms

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Correct Option: B
Explanation:

As NaCl is ionic compound so in molten states it will form $Na^+$ and $Cl^-$ ion and these ions conduct electricity.

Which impurity (as a salt) is associated with table salt obtained from sea-water?

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. $NaHCO _3$

  2. $MgCO _3$

  3. $MgCl _2$

  4. $NaI$

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Correct Option: C
Explanation:

Sea water contains $MgCl _2$ brine so salt made from sea water contains this as impurity.
sea salt:

 Chloride $(Cl^-)$  55.03%
 Sodium $(Na^+)$  30.59%
 Sulfate $(SO _4^{2-}$ 7.68% 
 Magnesium $(Mg^{2+})$ 3.68% 
 Calcium $(Ca^{2+})$ 1.18% 
 Potassium $(K^+)$ 1.11% 
 Bicarbonate $(HCO _3^-)$ 0.41% 
 Bromide $(Br^-)$ 0.19% 

The metal whose hydroxide does not decompose on heating but its nitrate decomposes is:

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. $Ca$

  2. $Al$

  3. $Na$

  4. $Fe$

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Correct Option: C
Explanation:

$NaOH \xrightarrow {heat} $ no reaction
$NaNO _3 \xrightarrow {heat} NaNO _2+\frac{1}{2}O _2$

The metal whose hydroxide does not decompose on heating but its nitrate decomposes is sodium.

Sodium chloride imparts a yellow color to the Bunsen flame. This can be interpreted due to the :

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. low ionisation of energy of sodium

  2. sublimation of metalic sodium to give yellow vapour

  3. emission of excess energy absorbed as a radiation in the visible region

  4. photo sensitivity of sodium

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Correct Option: C
Explanation:
Sodium chloride imparts a yellow color to the Bunsen flame. This can be interpreted due to the emission of excess energy absorbed as a radiation in the visible region.
When an alkali or akaline earth metal (or its salt) is introduced in the flame, the valence electrons of the metal absorbs energy and are excited to the higher energy level. When excited electrons return to their ground state, they release the absorbed energy as visible light.

Commercial common salts become slightly damp on keeping. This is due to the fact that:

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. common salt is hygroscopic

  2. common salt contains some impurities which are hygroscopic

  3. common salt is efflorescent

  4. common salt is crystalline

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Correct Option: B
Explanation:

Commercial common salt commonly becomes slightly damp on keeping because common salt contains some impurities like ${MgCl _2}$ and ${CaCl _2}$ which are hygroscopic in nature and absorb moisture from the atmosphere.
Hence, option B is correct.

Which one of the following products is formed when a mixture of steam, sulphur dioxide gas and oxygen gas (from air) is passed over dry lumps of common salt, the sodium chloride?

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. $ Na _2SO _3 $

  2. $ Cl _3 $

  3. $ NaHSO _3 $

  4. $ Na _2SO _4 $

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Correct Option: D
Explanation:

Hargreaves process:
$ 4NaCl (s) + 2SO _2 (g) + 2H _2O (g) + O _2 (g) \longrightarrow 2Na _2SO _4 + 4HCl $

Reaction, $Cl _2 + 2NaOH \rightarrow P$            

What are the products?

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. $NaCl + NaOCl + H _2$

  2. $NaCl + NaOCl + H _2O _2$

  3. $NaCl + NaOCl + H _2O$

  4. $NaCl + NaOCl + O _2$

Show answer
Correct Option: C
Explanation:

The reaction of non-metals with bases is complex. Example: When chlorine reacts with a base like sodium hydroxide, it gives multiple products like sodium hypochlorite, sodium chloride and water.

$Cl _2 + 2NaOH \rightarrow NaCl + NaOCl + H _2O$

The commercial salt is purified by passing :

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. $H _2S$ gas through an alkaline solution ofsalt

  2. HCI gas through a saturated solution of salt

  3. $H _2$ gas through a solution of salt

  4. $CI _2$ gas through a saturated solution of salt

Show answer
Correct Option: B
Explanation:

The common table salt is prepared by passing HCI gas through a saturated solution of salt. The precipitation is due to common ion effect.

$\underset { Salt\,solution }{ NaCl }+H^++Cl^-\longrightarrow  \underset { ppt}{ NaCl } $

Hence, option B is correct.

Statement 1: One mole of NaCl contains $2$ moles of ions.
Statement 2: NaCl is a stable salt at room temperature.

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  2. Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

  3. Statement 1 is correct but Statement 2 is not correct.

  4. Statement 1 is not correct but Statement 2 is  correct.

  5. Both the Statement 1 and Statement 2 are not correct

Show answer
Correct Option: B
Explanation:

Option (B) is correct.

Statement 1:  One mole of $NaCl$ contains 2 moles of ions i.e. a mole of chloride and a mole of sodium.Every $NaCl$ molecules has a $Na$ and a $Cl^-$ atom. So, if you have $6.022x10^{23}$ molecules, you will have that same number of $Na$ atoms and $Cl^-$ atoms, and by definition, 1 mole is $6.022x10^{23} $atoms.

Statement 2: $NaCl$ is a stable salt at room temperature.Sodium and chlorine forms a strong ionic bond, completing the octet of both atoms.They are arranged in a face centered cubic crystal structure where each $Na^+$ or $Cl^-$ ion is surrounded by 6 of the opposite ions forming an octahedron. This makes sodium chloride a stable compound.

Statement 1: Crystals of sodium chloride go into aqueous solution as ions.
Statement 2: The sodium ion has a $1+$ change and the chloride ion has a $1-$ charge and they are hydrated by the water molecules.

chemistry substances in common use salts and their properties study of some important salts salts used in daily life

  1. Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.

  2. Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.

  3. Statement 1 is correct but Statement 2 is not correct.

  4. Statement 1 is not correct but Statement 2 is correct.

  5. Both the Statement 1 and Statement 2 are not correct.

Show answer
Correct Option: A
Explanation:

Statement 1: Crystals of sodium chloride go into aqueous solution as ions.
$\displaystyle NaCl \rightleftharpoons Na^+ (aq) + Cl^- (aq) $
Statement 2: The sodium ion has a $1+$ change and the chloride ion has a $1−$ charge and they are hydrated by the water molecules.
Each sodium ion ( or each chloride ion) is surrounded by several water molecules.
Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.