Cement is mixed with water, it sets into a hard mass due to:
A. Hydration
B. Evaporation
C. Oxidation
D. Reduction
Answer: Option A
Solution (By JKExamLibrary)
Cement compounds react with water (hydration) forming hydrated silicates and aluminates, which crystallize and interlock, giving strength. This is exothermic.
Explanation:
Henry Moseley established that the properties of elements are periodic functions of their atomic numbers, not atomic masses. This refined Mendeleev's table and resolved anomalies like Ar-K. The modern periodic table is thus based on Moseley's work. Mendeleev proposed the original table based on atomic masses. Newlands gave Law of Octaves. Meyer plotted atomic volume curve.
Explanation:
Zn + H₂SO₄ → ZnSO₄ + H₂↑. Hydrogen gas is released, which burns with a pop sound. This is a test for hydrogen. Metals above hydrogen in reactivity series displace it from acids. Dilute H₂SO₄ with Zn produces H₂; with Cu, no reaction.
Explanation:
Graphite conducts electricity due to delocalized electrons within its layers. Diamond is an insulator. Buckminsterfullerene (C₆₀) is a semiconductor but not as good a conductor as graphite in bulk; fullerene solids can be doped to become conductors. Charcoal is a poor conductor. Graphite electrodes are used in batteries and electrolysis.
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