Ionic Equilibrium In Solution

Step 1: Concept
This involves the common ion effect in a weak base/salt system.
Step 2: Analysis
Adding (common ion ) suppresses the ionization of . This leads to a lower concentration of ions.
Step 3: Conclusion
A decrease in hydroxide ion concentration leads to a decrease in pH.
Final Answer: (C)

Step 1: Concept
Precipitation requires ionic product to exceed .
Step 2: Analysis
With and , threshold is .
Step 3: Conclusion
It precipitates when is more than .
Final Answer: (C)

Step 1: Concept
.
Step 2: Analysis
* Mol. wt of Oxalic acid . * Eq. wt (basicity = 2). * . (Note: calculation based on provided source 1885).
Step 3: Conclusion
Normality .
Final Answer: (B)

Step 1: Concept
In titrations, the indicator must change color at the pH of the equivalence point.
Step 2: Analysis
is a strong base and oxalic acid is a weak acid. The equivalence point will be in the alkaline range.
Step 3: Conclusion
Phenolphthalein is suitable as it changes color in the alkaline medium.
Final Answer: (B)

Step 1: Concept
This involves the common ion effect in a weak base/salt system.
Step 2: Analysis
Adding (common ion ) suppresses the ionization of . This leads to a lower concentration of ions.
Step 3: Conclusion
A decrease in hydroxide ion concentration leads to a decrease in pH.
Final Answer: (C)

Step 1: Calculate Milliequivalents
Total milliequivalents . Total milliequivalents .
Step 2: Find Concentration
Net left milliequivalents. .
Step 3: Calculate pH
.
Final Answer: (b)

Step 1: Definition
In a common emitter (CE) amplifier, the emitter is common to both input and output.
Step 2: Configuration
The input signal is fed into the base terminal.
Step 3: Conclusion
Thus, the input is applied across the base-emitter junction.
Final Answer: (d)

Step 1: Effect of Plate
Introducing a glass plate shifts the entire fringe pattern.
Step 2: Fringe Width Independence
Fringe width depends on wavelength, slit separation, and screen distance.
Step 3: Conclusion
Since these parameters do not change when the plate is added, the fringe width remains unchanged at 0.3 mm.
Final Answer: (b)

Step 1: Law Principle
Wien's displacement law states that the wavelength of maximum emission ( ) is inversely proportional to the absolute temperature ( ).
Step 2: Application
By measuring the color (wavelength) of light from a star, scientists can calculate its surface temperature.
Step 3: Formula
, where is Wien's constant.
Final Answer: (b)

Step 1: Open Tube
Fundamental frequency .
Step 2: Closed Tube Formation
Immersion turns it into a closed tube. Remaining air length .
Step 3: New Frequency
New fundamental frequency .
.
Final Answer: (a)

Step 1: Concept
The dissociation of water ( ) is an endothermic process.
Step 2: Temperature Effect
As temperature increases, the dissociation constant ( ) increases, leading to a higher concentration of ions.
Step 3: pH Relation
Since , a higher concentration of results in a lower pH value.
Step 4: Conclusion
Neutral water has a pH of 7.0 at . A pH of 6.5 for neutral water implies the temperature is higher than .
Final Answer: (B)

Step 1: Analysis
is an extremely dilute basic solution.
Step 2: Water Contribution
In such dilute solutions, the from the self-ionization of water ( ) cannot be ignored.
Step 3: Total Concentration
Total .
Step 4: Calculation
. .
Final Answer: (D)

Step 1: Understanding the pH scale.
pH is the negative logarithm of the hydrogen ion concentration: A change in pH by 3 units corresponds to a change in the H ion concentration by a factor of 1000.

Step 2: Explanation of the options.
- (1) Reduced to half: Incorrect, as pH change of 3 units changes the concentration by a factor of 1000.
- (2) Doubled: Incorrect, pH change does not double the concentration.
- (3) Reduced by 1000 times: Correct. An increase of 3 pH units corresponds to a 1000 times reduction in H ion concentration.
- (4) Increased by 1000 times: Incorrect, as the concentration decreases by 1000 times.

Step 3: Conclusion.
The correct answer is (3) Reduced by 1000 times.

Step 1: Understanding the solubility product.
The solubility product ( ) of BaCl is given by: Let the solubility of BaCl be . The concentration of will be , and the concentration of will be (because there are two chloride ions for each BaCl ).

Step 2: Setting up the equation.
Substitute the concentrations into the solubility product expression: We are given . So: Taking the cube root:

Step 3: Conclusion.
The solubility of BaCl is mol/L.

Step 1: Identifying Lewis acids.
A Lewis acid is a substance that can accept a pair of electrons. This typically happens when the species has an empty orbital that can accept an electron pair.

Step 2: Explanation of the options.
- (1) NaCl: Sodium chloride is an ionic compound and does not have an electron-deficient center.
- (2) MgCl : Magnesium chloride is also not a Lewis acid; it is a simple ionic compound.
- (3) AlCl : Aluminum chloride is a Lewis acid because the aluminum atom has an empty orbital and can accept an electron pair.
- (4) SnCl : Tin chloride is also a Lewis acid, but it is less strongly acidic than AlCl .

Step 3: Conclusion.
The correct answer is (3) AlCl .

Step 1: Formula / Definition}

Step 2: Calculation / Simplification}
Most endothermic in reverse direction most exothermic in forward direction.
Diagram (b) shows largest drop in for forward reaction.
Reverse reaction has highest positive .
Step 3: Final Answer

Step 1: Formula / Definition}

Step 2: Calculation / Simplification}




Step 3: Final Answer

Step 1: Formula / Definition}

Step 2: Calculation / Simplification}
Exp 1 \& 2: constant, doubles rate doubles
Exp 3 \& 4: constant, doubles rate doubles

Step 3: Final Answer

Concept: Acid strength in hydrogen halides increases down the group due to decrease in bond strength.

Step 1: Bond strength order:

Step 2: Reason: Stronger bond → harder to release H → weaker acid.

Step 3: HF has strongest H–F bond. Conclusion:
Thus, HF is the weakest acid.

Concept: Normality depends on the number of replaceable H ions. For polyprotic acids:

Step 1: Identify nature of acid: H PO is triprotic (3 replaceable H ).

Step 2: Different stages of neutralization:

• First stage:
• Second stage:
• Third stage:

Step 3: All these normalities are possible depending on extent of neutralization.
Conclusion:
All given values are possible.

Concept: Basicity depends on availability of lone pair

Step 1: In (a), N is sp hybridized → lone pair freely available.

Step 2: In (b), lone pair is in aromatic ring → less available.

Step 3: In (c), lone pair is partially delocalized.

Step 4: In (d), O is more electronegative → holds lone pair tightly.
Conclusion:
Most basic = option (a)

Concept: Conjugate base strength inverse of acid strength

Step 1: More oxygen → stronger acid due to resonance.

Step 2: Acid strength order:

Step 3: Hence conjugate base strength: Conclusion:
Strongest base = ClO

Concept: Acid-base neutralization + excess OH determines pH

Step 1: Moles of H SO :

Step 2: H SO gives 2H :

Step 3: Moles of KOH:

Step 4: Excess OH :

Step 5: [OH ] concentration:

Step 6: pOH and pH: Conclusion:
pH = 10.9

Step 1: Understanding the Concept:
A conjugate base is formed when an acid donates a proton (H ).
Step 2: Detailed Explanation:
H S H + HS When H S loses one proton, it forms HS . HS is the conjugate base of H S.
S is the conjugate base of HS .
Step 3: Final Answer:
The conjugate base of H S is HS , option (A).

Step 1: Understanding the Concept:
This is a strong acid-strong base neutralization. The pH is determined by the concentration of H ions remaining after reaction.
Step 2: Detailed Explanation:
Volume of HCl = 50 cc = 0.05 L, Molarity = 1 M. Moles of H = mol. Volume of NaOH = 30 cc = 0.03 L, Molarity = 1 M. Moles of OH = mol. Reaction: . Moles of H remaining = mol. Total volume = L. M. pH = .
Step 3: Final Answer:
pH = 0.6021, option (B).

Step 1: Understanding the Concept:
Henderson-Hasselbalch equation for acid buffer.
Step 2: Detailed Explanation:
is the correct equation.
Step 3: Final Answer:
The correct expression is .

Step 1: Understanding the Concept:
pH = .
Step 2: Detailed Explanation:
Moles of HCl = mol. Molarity = M. M. pH = .
Step 3: Final Answer:
pH = 2.

Step 1: Understanding the Concept:
is product of ion concentrations raised to their stoichiometric coefficients.
Step 2: Detailed Explanation:
, so .
Step 3: Final Answer:
.

Step 1: Understanding the Concept:
Strong acid-strong base titration curve.
Step 2: Detailed Explanation:
pH starts low, rises slowly, then jumps sharply at equivalence point (pH=7), then levels off.
Step 3: Final Answer:
Graph A shows correct titration curve.

Step 1: Understanding the Concept:
Mole fraction = moles of component/total moles.
Step 2: Detailed Explanation:
Moles H = 1/2 = 0.5 mol
Moles O = 8/32 = 0.25 mol
Total = 0.75 mol

Step 3: Final Answer:
Mole fraction is 0.667.

Step 1: Understanding the Concept:
, .
Step 2: Detailed Explanation:



Step 3: Final Answer:
Elevation is 0.0512°C.

Step 1: Understanding the Concept:
.
Step 2: Detailed Explanation:
,

Step 3: Final Answer:
.

Step 1: Understanding the Concept:
CaF dissociates as Ca + 2F .
Step 2: Detailed Explanation:
,

Step 3: Final Answer:
Solubility product is .

Concept: Lower means stronger acid. The ortho effect enhances acidity.

Step 1: Ortho effect. In o-hydroxy benzoic acid (salicylic acid), the -OH group is ortho to -COOH. It forms an intramolecular hydrogen bond with the carboxylate ion after deprotonation, stabilizing the conjugate base.

Step 2: Comparison.
• o-hydroxy benzoic acid: Intramolecular H-bond stabilizes conjugate base → strongest acid → lowest .
• m- and p-hydroxy benzoic acids: No intramolecular H-bond; electronic effects (resonance/inductive) but less effective than ortho effect.
• Benzoic acid: No additional -OH group → weakest acid among these.

Concept: Buffer formula:

Step 1: Given.
Equal concentrations log term = 0

Step 2: Convert pH to pOH.

Concept: Neutralization:

Step 1: Moles.


Step 2: Stoichiometry.
Required HCl: Available HCl = 0.1 → insufficient

Step 3: Conclusion.
remains → solution is basic.

Concept: For a weak acid:

Step 1: Given:

Step 2: