Which of the following statements is FALSE? Core electrons shield valence electr

Question

Which of the following statements is FALSE? Core electrons shield valence electrons strongly. Z_eff in a Cl" ion is less than Z_r in a Cl atom. More total electrons result in a greater amount of shielding. A Cl^- ion has the same number of protons as a Cl atom. A Cl atom has fewer core electrons than a ion. Consider the following chemical reaction: 2 CO (g) + O_2 (g) rightarrow 2 CO_2 (g). Given the bond enthalpy values shown In the table to the right, what is AH for this reaction? - 557 kj/mol -1041 kj/mol -1099 kj/mol -1996 kj/mol -1641 kj/mol

Explanation / Answer

Ans 3. Option E is wrong because number of core electrons are equal in Cl and Cl-.

            Core electrons are the electrons which are present in inner shells. In case of Cl-, the extra electron enters into the valence shell.

Ans 4. For the reaction,

           rH = B.E. of reactants - B.E. of products                .........(B.E. is bond enthalpy)

                  = [2x B.E. of CO bond + B.E. of O=O bond] – [4x B.E. of C=O bond]

                  = [2 x 1070 + 498.7] – [ 4 x 799 ]

                  = 2638.7 – 3196

                  = -557.3 kJ/mol

So, option A is correct.

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