The oxidation state of Cr in potassium dichromate (K2Cr2O7) is:
A. +3
B. +7
C. +2
D. +6
Answer: Option D
Solution (By JKSSB Mock Tests)
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:
Urea (CO(NH₂)₂) is a nitrogenous fertilizer with the highest nitrogen content (about 46%). Superphosphate provides phosphorus, muriate of potash (KCl) provides potassium, and gypsum (CaSO₄·2H₂O) is a soil conditioner providing calcium and sulfur, not primary NPK nutrients.
Explanation:
Diamond is the hardest known natural substance. It consists of each carbon atom covalently bonded to four other carbon atoms in a rigid tetrahedral 3D lattice, making it extremely hard. Graphite is soft due to its layered structure with weak van der Waals forces between layers.
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