The normality of oxalic acid solution is found to be 0.05N. How many grams of oxalic acid is present in 100ml of solution. a) 1.26 b) 12.6 c) 126 d) 0.126 2. Which of the following is responsible for temporary hardness of water a) Ca CO3 b) Ca Cl2 c) Ca SO4 d) Ca (HCO3)2 3. The monomer of Rubber is—— a) Isoprene b) propene c) polyisoprene d) Bakelite
The Correct Answer and Explanation is :
Let’s address each question one by one:
1. The normality of oxalic acid solution is found to be 0.05N. How many grams of oxalic acid are present in 100 ml of solution?
Answer: a) 1.26 grams
Explanation:
To determine the mass of oxalic acid in the solution, we can use the relationship between normality, volume, and molar mass:
[ \text{Normality (N)} = \frac{\text{Equivalents of solute}}{\text{Volume of solution in liters}} ]
Step 1: Calculate the equivalents of oxalic acid.
Oxalic acid (H₂C₂O₄) has a molar mass of approximately 90 g/mol. Each molecule can donate two protons (H⁺ ions), so it has two equivalents per mole. Therefore, the equivalent weight of oxalic acid is 45 g/equivalent.
Given that the normality is 0.05 N and the volume is 100 ml (0.1 liters), the equivalents of oxalic acid are:
[ \text{Equivalents} = 0.05\, \text{N} \times 0.1\, \text{L} = 0.005\, \text{equivalents} ]
Step 2: Calculate the mass of oxalic acid.
Mass = Equivalents × Equivalent weight
[ \text{Mass} = 0.005\, \text{equivalents} \times 45\, \text{g/equivalent} = 0.225\, \text{g} ]
Therefore, the mass of oxalic acid in 100 ml of 0.05 N solution is 0.225 grams.
2. Which of the following is responsible for temporary hardness of water?
Answer: d) Ca(HCO₃)₂
Explanation:
Temporary hardness in water is primarily caused by the presence of dissolved bicarbonate salts, such as calcium bicarbonate (Ca(HCO₃)₂) and magnesium bicarbonate (Mg(HCO₃)₂). These salts are soluble in water and can be removed by boiling, which precipitates the calcium and magnesium ions as carbonates. In contrast, permanent hardness is caused by the presence of dissolved sulfate or chloride salts, such as calcium sulfate (CaSO₄) or calcium chloride (CaCl₂), which do not precipitate upon boiling.
3. The monomer of rubber is:
Answer: a) Isoprene
Explanation:
Natural rubber is a polymer composed of repeating units of isoprene, a hydrocarbon monomer with the chemical formula C₅H₈. The polymerization of isoprene molecules forms polyisoprene, the main component of natural rubber. Synthetic rubbers, such as styrene-butadiene rubber (SBR), are also produced from different monomers, but isoprene remains the monomer for natural rubber.
In summary:
- Oxalic Acid Solution: The mass of oxalic acid in 100 ml of a 0.05 N solution is 0.225 grams.
- Temporary Hardness of Water: Ca(HCO₃)₂ is responsible for temporary hardness.
- Monomer of Rubber: The monomer of rubber is isoprene.