Explanation

Oxidation number of Cr in Na2Cr2O7:

Let oxidation number of Cr = x

2(Na) + 2(Cr) + 7(O) = 0

2(+1) + 2(x) + 7(-2) = 0

2 + 2x -14 = 0

2x = 12

x = +6

Last verified on 25-10-2026

Explanation

• Antimony is a chemical element with the symbol Sb and atomic number 51.
• The symbol Sb comes from the Latin name Stibium.
• Antimony is a metalloid used in alloys, flame-retardant materials, and some semiconductor applications.

Additional information:

• Au — Gold: Atomic number 79.
• Ag — Silver: Atomic number 47.
• Fe — Iron: Atomic number 26.
• Na — Sodium: Atomic number 11.
• K — Potassium: Atomic number 19.

Last verified on 25-10-2026

Explanation

• Hess's law states that the total enthalpy change of a chemical reaction is the same regardless of whether the reaction takes place in one step or several steps.
• Enthalpy change depends only on the initial reactants and final products, not on the pathway followed by the reaction.
• The law is based on the fact that enthalpy is a state function, meaning its value depends on the initial and final states.

Last verified on 25-10-2026

Explanation

• The addition of HCl to propene is an electrophilic addition reaction.
• The H⁺ ion attacks the double bond first, forming a more stable carbocation intermediate.

Last verified on 25-10-2026

Explanation

• The M²⁺ ion has 24 electrons (2 + 8 + 14 = 24). Since it has lost 2 electrons, the atomic number of M is 26.
• Number of neutrons = Mass number − Atomic number = 56 − 26 = 30.
• Therefore, the nucleus contains 30 neutrons.

Last verified on 25-10-2026