Lakshya Education MCQs

Question: Dilute hydrochloric acid (HCl) reacts with metals to evolve _____ gas along with the formation of corresponding metal salt.
Answer: Option B
: B

Acidsreact with metals to producetherespective metalsaltalong withhydrogen gas. The general form of the reaction is given below:

Acid (aq)+Metal (s)Salt(aq)+Hydrogen (g)

For example:
When hydrochloric acid reacts with zinc, itproduceszinc chloride along with the evolution ofhydrogen gas.

The chemical reaction is given below:

2HCl (aq)+Zn (s)ZnCl2(aq)+H2(g)

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Question 1. Which of the following will behave as a strong acid when added to water?
  1.    C2H5COOH
  2.    H2SO4
  3.    HCOOH
  4.    CH3COOH
Answer: Option B
: B

Strength of acid depends on the ability of the compound to donate the proton and thenumber of protons it can donate inthe solution. Among all the given acids H2SO4 has maximum ability to donate H+ in the aqueous solution. Also, H2SO4 can donate two H+ ions per molecule while all other acids can donate only one H+ ion in the solution. Hence,H2SO4 is the strongest acid among the given acids.
Question 2. Which of the following types of medicine is used for the treatment of indigestion?
  1.    Antibiotic
  2.    Analgesic
  3.    Antacid
  4.    Antiseptic
Answer: Option C
: C

Indigestion causes acidity in the stomach. We add anti-acids to neutralise it. The antacids are basic in nature and hence neutralise the acids. Magnesium hydroxide (milk of magnesia) is a commonly used antacid.
Question 3. Which of the following have the highest pH value?
  1.    Battery acid
  2.    Water
  3.    Vinegar
  4.    Soda
Answer: Option B
: B

Battery acid, vinegar and soda are all acids from the given options.All acids have pH value less than 7. Battery acid and vinegar have pH values of 0.8 and 2.4 respectively. The pH value of soda ranges from approximately 2.2 to 3.3.
Water has a pH value of 7 if there are no impurities in it.
Hence from the given options, water has the highest pH value.
Question 4. Which of the following is a neutralisation reaction?
  1.    NaOH(aq) + HCl(aq)→ NaCl(aq) + H2O(l)
  2.    2HCl(aq) + 2Na(s) → 2NaCl(aq) + H2(g)
  3.    Na2CO3(aq) + H2O(l) → 2NaOH(aq) + CO2(g)
  4.    NH3(aq) + H2O(l) → NH4OH(aq)()
Answer: Option A
: A

When an acid reacts with a base, it forms salt and water. This is called neutralisation reaction.
Here, only the reaction between hydrochloric acid with sodium hydroxide is a neutralisation reaction since it gives sodium chlorideand water as products. The reaction involved is given below:

Question 5. What happens to the solubility of a saturated solution of NaCl, when a current of HCl gas is passed through it?
  1.    Increases 
  2.    Decreases 
  3.    Remains unchanged
  4.    Decomposes NaCl
Answer: Option B
: B

When HCl gas is passed through a saturatedNaClsolution, the number of Cl1 ions increases. The increased number ofCl1 interact with Na+1 ions to form crystallised NaCl. Thus, the solubility of NaCl decreases and it is recovered in crystalline form. This phenomenon is called "common ion effect".

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