The enthalpy of formation of water is –285.8 kJ/mol. What can be inferred from this statement?

Answer;

As and Sr ------- [Kr]

Be ------------- [He]

O and Mg ------- [Ne]

S and Ca ------- [Ar]

Explanation

• The Be+ ion has 2 electrons, matching He. The Mg2+ and O2− ions possess 10 electrons each, like Ne.
• S2− and Ca2+ ions each have 18 electrons, the same as Ar. The As3− and Sr+ ions hold 36 electrons, paralleling Kr.
• Elements gain or lose electrons to reach a stable electron configuration akin to that of noble gases.
• When atoms lose electrons, they form positive ions (cations), and when they gain electrons, they form negative ions (anions).

Answer: A= 0.5, B = 0.25, C = 0.125, D = 0.015625 and E = 0.00390625

Explanation:

The half-life of a substance refers to the duration it takes for that substance to decrease to half of its original quantity.

Here, n signifies the count of half-lives.

The remaining quantity of the substance after n half-lives can be determined using the formula provided,

When n = 1,

Fraction of substance remaining = 0.5¹ = 0.5.

This indicates that after the first half-life, the remaining quantity is half of the original amount.

Thus, we find A = 0.5

<pfor n="2," we="" calculate=""><pso after="" two="" half-lives="" the="" remaining="" quantity="" is="" of="" original=""><phence>B = 0.25 <pfor n="3," we="" have=""><pso after="" three="" half-lives="" the="" remaining="" amount="" is="" of="" original.=""><ptherefore we="" find="">C = 0.125<pfor n="6," we="" see="">

Thus, D = 0.015625

<pfor n="8," we="" calculate=""><pconsequently>E = 0.00390625

The calculated values for A, B, C, D, and E are 0.5, 0.25, 0.125, 0.015625, and 0.00390625 respectively.

</pconsequently></pfor></pfor></ptherefore></pso></pfor></phence></pso></pfor>

The accurate answer is option 2. When Pt2+ undergoes reduction, it loses electrons, thus oxidizing itself. The oxidation state corresponds to the atom's charge. When an electron is added, the overall charge diminishes, which in turn reduces the oxidation number.

The right answer is 2.