Identify each of the following as a representative element or a transition element.
a) lithium
b) platinum
c) promethium
d) carbon

The Representative elements are the first two relations and the last six relations of the Periodic Table. The Transition elements  are in three series in periodic table and they all are metals.
therefore,
A) lithium is Representative element
B) platinum isTransition element
C) promethium isTransition element
D) carbon is Representative element

Answer:             1.0  × 10⁻⁵ msolution:                     as we know ph is given as,                                    ph  = -log [h⁺]and,                                    [h⁺]  =  10^-ph    (1)putting value of ph in eq. 1,                                    [h⁺]  =  10⁻⁵                                    [h⁺]  =  1.0  × 10⁻⁵ m

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