Some Basic Concepts Of Chemistry

C_nH_2n + 1.5nO2 → nCO₂ + nH₂O
6X1.5n= 27
n= 3
So , the correct answer is (B) : Propene

Step 1: Analyze Assertion (A)
In volumetric analysis, the concentration of the solutions used must be known accurately. KOH solutions are commonly used as titrants in acid-base titrations. The concentration of a KOH solution can change over time due to various factors. Therefore, it’s crucial to check and standardize its concentration before use. Assertion (A) is correct.
Step 2: Analyze Reason (R)
KOH solutions absorb atmospheric carbon dioxide ( ). The reaction between KOH and forms potassium carbonate ( ) and water:

This reaction consumes KOH, reducing its concentration in the solution. Hence, Reason (R) is correct.
Step 3: Analyze the Relationship between (A) and (R)
The absorption of atmospheric by KOH solution directly affects its concentration. This is the primary reason why the concentration of a KOH solution needs to be checked before use, especially if it’s an older solution. Thus, Reason (R) is the correct explanation for Assertion (A).

Mass of Sugar = (25 × 250) + (40 × 500)
= 262.5 gm

Correct answer is 35%.

In complete combustion, the organic compound reacts with oxygen to produce CO₂ and H₂O. From the masses of CO₂ and H₂O produced, we can calculate the masses of carbon and hydrogen in the compound.

Step 1: Calculate the mass of carbon

From the mass of CO₂, we can find the mass of carbon in the compound. The molar mass of CO₂ is 44 g/mol, and the molar mass of carbon (C) is 12 g/mol. The mass of carbon in CO₂ is proportional to the molar masses: We are given that the percentage of carbon in the compound is 24%. Hence, the total mass of the organic compound can be found by:

Step 2: Calculate the mass of hydrogen

Next, we calculate the mass of hydrogen in the compound. The molar mass of H₂O is 18 g/mol, and the molar mass of hydrogen (H) is 1 g/mol. The mass of hydrogen in H₂O is proportional to the molar masses:

Step 3: Calculate the percentage of hydrogen

The percentage of hydrogen in the compound is: Thus, the percentage of hydrogen in the compound is 5.6%

Step 1: Understanding the Stability in Aqueous Solution

• K₂Cr₂O₇: Potassium dichromate is more stable in aqueous solution, making it suitable as a primary standard.
• Na₂Cr₂O₇: Sodium dichromate is less stable in water and tends to undergo changes in concentration, making it less suitable as a primary standard.

Conclusion for Statement I: K₂Cr₂O₇ is preferred as a primary standard. Statement I is true.

Step 2: Solubility Comparison

• K₂Cr₂O₇: Less soluble in water compared to Na₂Cr₂O₇.
• Na₂Cr₂O₇: More soluble in water than K₂Cr₂O₇.

Conclusion for Statement II: Statement II is false because K₂Cr₂O₇ is less soluble than Na₂Cr₂O₇.

Final Answer:

Statement I is true, but Statement II is false.

Reaction of BaCl₂ and Na₃PO₄

Given Reaction:

The reaction between BaCl₂ and Na₃PO₄ is:

3BaCl₂ + 2Na₃PO₄ → Ba₃(PO₄)₂ + 6NaCl

Given Moles:

• Barium chloride (BaCl₂): 5 moles
• Sodium phosphate (Na₃PO₄): 3 moles

Calculation:

The balanced equation shows that 3 moles of BaCl₂ react with 2 moles of Na₃PO₄ to produce 1 mole of Ba₃(PO₄)₂.

Now, using the mole ratio from the equation:

• From 3 moles of BaCl₂, 1 mole of Ba₃(PO₄)₂ is formed.
• So, from 5 moles of BaCl₂, the moles of Ba₃(PO₄)₂ formed will be: 5 moles × (1 mole Ba₃(PO₄)₂ / 3 moles BaCl₂) = 5/3 = 5 moles.

Conclusion:

The number of moles of Ba₃(PO₄)₂ formed is 5 moles.

To answer the given question, we need to identify the most appropriate purification technique for a steam volatile and water-immiscible substance.

Let's consider each option:

1. Fractional distillation: This method is used for separating mixtures of liquids with different boiling points, primarily when they are miscible with each other. This is not suitable for substances that are water-immiscible and require separation based on steam volatility.
2. Fractional distillation under reduced pressure: This technique is used to distill compounds at a temperature lower than their boiling points by reducing the pressure. It is suitable for heat-sensitive substances but not specifically for steam volatile substances that are water-immiscible.
3. Distillation: This is a general method of separating mixtures based on differences in their volatilization (evaporation at their boiling point). Regular distillation does not take advantage of steam volatility, making it unsuitable for the given requirement.
4. Steam distillation: This process is specifically designed for purifying steam volatile and water-immiscible substances. The technique involves passing steam through the mixture, causing the volatile compounds to vaporize at temperatures lower than their actual boiling points due to the presence of steam, which is a key advantage when dealing with such substances.

Therefore, the correct answer is Steam distillation. This method is ideal for the purification of steam volatile water-immiscible substances because it effectively separates volatile components without the need for their complete boiling and without them being miscible in water.

Hence, the chosen technique, steam distillation, takes advantage of the volatility of the substance in the presence of steam, allowing it to be collected separately in a cooled receiver.

The question asks about the appropriate method for extracting essential oils from flowers. Essential oils are steam volatile organic compounds and are generally insoluble in water at room temperature but can mix with water vapour in the vapour phase. Let's analyze the options provided:

• Crystallisation: This process is typically used to purify solid substances. It is not suitable for extracting volatile liquids like essential oils.
• Distillation under reduced pressure: This technique, also known as vacuum distillation, is used to distill at lower temperatures for substances that decompose at higher temperatures. While it helps with temperature-sensitive substances, it is not the specific choice for compounds that can mix directly with steam.
• Distillation: Regular distillation involves heating the mixture to separate volatile components. This is used more broadly for substances that are easily vaporized. Essential oils require specific conditions due to their affinity with steam.
• Steam distillation: This method is specifically used for extracting volatile compounds from non-volatile mixture parts. It involves the passage of steam through the plant material, where the essential oils are vaporized along with the steam, then condensed and separated.

Based on the description of essential oils' properties—being steam volatile and mixing with water vapour—steam distillation is the most appropriate method. This technique allows the oils to vaporize at lower temperatures, preserving their delicate structure and aroma.

Thus, the correct answer is steam distillation.

To solve the given question, we need to match each technique listed in LIST I to its correct application in LIST II. Let's analyze each technique and their most common applications:

1. Distillation: This technique is used for the separation of volatile components based on differences in their boiling points. In the question, option IV. Chloroform-Aniline matches with distillation, as this method can separate components with different boiling points.
2. Fractional Distillation: This method is an enhanced form of distillation that is used when separating mixtures of liquids with closer boiling points. It is commonly used in III. Separation of crude oil fractions because crude oil consists of many components with similar boiling points.
3. Steam Distillation: This technique is used for purifying temperature-sensitive compounds such as essential oils and certain aromatic compounds. It suits II. Aniline - Water mixture as it helps in separating compounds that are insoluble in water and have a high boiling point.
4. Distillation under Reduced Pressure: This technique is used for liquids that decompose at high temperatures. Lowering the pressure allows the distillation process to occur at lower temperatures, suitable for I. Separation of glycerol from spent-lye, where glycerol needs to be separated without decomposition.

Now, let's match LIST I with LIST II correctly:

Thus, the correct solution is: A-IV, B-III, C-II, D-I.