Chemistry

Acids and Bases

594 Questions

Acids and bases questions cover the chemical properties, common examples, and theoretical concepts of acidic and basic substances. Topics include identifying proton acceptors, recognizing amphoteric substances, and knowing the sources of everyday organic acids. These foundational chemistry questions are common across SSC, banking, and railways examinations.

Acid and base propertiesOrganic acidsAmphoteric substancesProton donors and acceptorsChemical formulas

Acids and Bases Questions

Multiple choice biology windows of knowledge human tongue organ of taste tongue : the organ of taste
The food tastes sour when

  1. Hydrogen ion pass through the same channel as that of the sodium ion

  2. Hydrogen ion blocks the potassium channel

  3. Hydrogen ion blocks the calcium channel

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The sour taste originally comes from acidic foods, in which their molecules dissociate into proton/positive hydrogen ions. Common chemical molecules that dissociate into hydrogen ions to characterize a sour or tangy taste are carboxylic acids which have a distinctive carboxyl functional group, -COOH. The hydrogen proton of acids and sour foods can influx through the Na$^+$ channels, or through a proton transport membrane protein. Some acids block the efflux of K$^+$ at the microvilli. The resulting influx of protons or a reduction in K$^+$ conductance will initiate receptor potentials in response to the quality of sour tastes.
So, the correct answer is option D.
Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Which has peroxy linkage ?

  1. Perchloric acid

  2. Hypochlorous acid

  3. Para perchloric acid

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Perchloric acid is a mineral acid with the formula HClO₄. Usually found as an aqueous solution, this colorless compound is a stronger acid than sulfuric acid and nitric acid

Hypochlorous acid  $HOCl$ is a weak acid that forms when chlorine dissolves in water, and itself partially dissociates, forming hypochlorite,

| Oxidation state of the halogen inthe acid |                                Oxoacids |  Structure | | --- | --- | --- | | $Cl$ |  $Br$ |  $I$ | |  $+1$ | $HClO$  |  $HBrO$ |  $HlO$ |  $H-O-X$ | |  $+3$ | $HClO _2$ |   |   |  $H-O-x\to O$ | |  $+5$ | $HClO _3$  | $HBrO _3$  | $HlO _3$  |  $H - O - \overset{O}{\overset{\uparrow}{X}} \to O$ | |  $+7$ |  $HClO _4$ |  $HBrO _4$ | $HlO _4$  |  $HO - \underset{O}{\underset{\downarrow}{\overset{O}{\overset{\uparrow}{X}}}} \to O$ |
Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Chlorous acid is unstable and decomposes into :

  1. $\displaystyle { HCl,\quad { ClO } _{ 2 } }$
  2. $\displaystyle { HCl,\quad { Cl } _{ 2 } }$
  3. $\displaystyle { HOCl,\quad { ClO } _{ 2 } }$
  4. $\displaystyle { HOCl,\quad { Cl } _{ 2 } }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
It fresh solution is colourless but soon it turns yellow due to formation of $ClO _{2}$

$5HClO _{2}\rightarrow 4ClO _{2}+HCl+2H _{2}O$
Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Which one of the following oxy acid of fluorine exists ?

  1. $HOF$
  2. $HFO _{3}$
  3. $HFO _{4}$
  4. $HFO _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In fluorine d-orbitals are absent so it shows only +1 oxidation state in oxo-acid,
but not + 3, + 5 or + 7. 


That's why unlike other members (halogens) fluorine only forms one oxoacid HOF.

Hence, option A is correct.

Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Which of the following statements is not correct?

  1. All halogens except flourine from OXO-acids

  2. Hypohalous acids HOCI,HOBr and HOI are all strong acids

  3. Hypochlorous acid is the most stable among hypohalous acids

  4. Chlorous acid is the only halous acid known
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There are also other halous acids like:
$HOBr _2$ which is Hydrobromous acid.
So D is wrong

Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Which of the following is the correct statement? 

  1. $ SO _2 $ is anhydride of sulphuric acid
  2. $ NO _2 $ is anhydride of nitric acid
  3. $ Cl _2O _7 $ is anhydride of perchoric acid
  4. $ P _2O _5 $ is anhydride of orthophosphorus acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$Cl _2​O _7​+H _2​O⟶2HClO _4​$

Thus $Cl _2​O _7​$ is an anhydride of perchloric acid.

Option C is correct.
Multiple choice oxoacids of halogens p- block elements-ii p-block elements the p-block elements chemistry

Which of the following has more acidic in nature?

  1. HClO
  2. HClO$ _2$
  3. HClO$ _3$
  4. HClO$ _4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Acidity of oxyacids of halogen increases with increase in oxidation number of halogen Oxidation number of CI in HCIO is + 1, HCIO$ _2$ is +3, HClO$ _3$ is + 5 and HCIO$ _4$ is + 7.
$\therefore$ HClO$ _4$ is most acidic among given choices.
Multiple choice chemistry further aspects of equilibria dissociation constants ionisation of weak acids and weak bases ionization constants of weak acids and weak bases

Which of the following will supress the ionisation of acetic acid in aqueous solution?

  1. $NaCl$
  2. $HCI$
  3. $KCI$

  4. Unpredicatble
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.

So addition of $CH _3COONa$ to $CH _3COOH$ increases the $pH$ of solution but addition of $NH _4Cl$ to $NH _4OH$ decreases the $pH$ of solution.
Here, the addition of $HCl$ acid will suppress the ionisation of acetic acid.

Multiple choice chemistry further aspects of equilibria dissociation constants ionisation of weak acids and weak bases ionization constants of weak acids and weak bases

In the third group of qualitative analysis, the precipatitating reagent is $NH _4Cl / NH _4OH$. The function of $NH _4Cl$ is to 

  1. increase the ionisation of $NH _4OH$
  2. supress the ionisation of $NH _4OH$

  3. convert the ions of group third into their respective chlorides
  4. stabilise the hydroxides of group $III$ cations
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.

So, addition of $CH _3COONa$ to $CH _3COOH$ increases the pH of solution but addition of $NH _4Cl$ to $NH _4OH$ decreases the pH of solution.
So, the function of $NH _4Cl$ to suppress the ionisation of $NH _4OH$ and to reduce conentration of hydroxide ion in solution.

Multiple choice chemistry further aspects of equilibria dissociation constants ionisation of weak acids and weak bases ionization constants of weak acids and weak bases

Addition of $HCl$ will not suppress the ionization of:

  1. acetic acid

  2. benzoic acid
  3. ${H} _{2}S$

  4. sulphuric acid
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Any acid weaker than $HCl$ will be suppressed by $HCl$. Hence, among the given options, only sulphuric acid is an acid with comparable acidity strength to $HCl$. The same can also be verified using $K _a$ values from the data.