Write a balanced half-reaction for the reduction of dichromate ion Cr2O−27 to chromium ion Cr+3 in acidic aqueous solution. Be sure to add physical state symbols where appropriate.

14 H⁺(aq) + Cr₂O₇²⁻(aq) + 6 e⁻ → 2 Cr⁺³ + 7 H₂O(l)

Explanation:

Let's consider the half-reaction for the reduction of dichromate ion Cr₂O₇²⁻ to chromium ion Cr⁺³ in acidic aqueous solution.

Cr₂O₇²⁻(aq) → Cr⁺³

Step 1: Perform the mass balance adding H₂O(l) and H⁺(aq) where appropriate.

14 H⁺(aq) + Cr₂O₇²⁻(aq) → 2 Cr⁺³ + 7 H₂O(l)

Step 2: Perform the charge balance adding electrons where appropriate.

14 H⁺(aq) + Cr₂O₇²⁻(aq) + 6 e⁻ → 2 Cr⁺³ + 7 H₂O(l)

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.