B. Recrystallization of sodium carbonate from its aqueous solution
C. Heating baking soda
D. Reaction of NaCl with CaCO₃
Answer: Option B
Solution (By JKExamLibrary)
Sodium carbonate (soda ash) is dissolved in water and crystallized to obtain washing soda. Heating baking soda gives anhydrous sodium carbonate. Brine electrolysis gives NaOH, Cl₂, H₂. Solvay process makes Na₂CO₃.
Explanation:
In K2Cr2O7, potassium has an oxidation state of +1 and oxygen is -2. Let the oxidation state of Cr be x. The sum of oxidation states in a neutral molecule is zero: 2(+1) + 2(x) + 7(-2) = 0. Solving this gives 2 + 2x - 14 = 0, so 2x = 12, and x = +6.
Explanation:
Neutralization is the reaction of an acid and a base to form salt and water. HCl (acid) + NaOH (base) → NaCl (salt) + H₂O. Option A is combination; C is decomposition; D is displacement.
Explanation:
Gamma rays are high-energy electromagnetic waves with no mass and no charge. They have the highest penetrating power among alpha, beta, and gamma rays, requiring thick lead or concrete to be stopped. Alpha is stopped by paper, beta by aluminum foil.
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