Given that #[Au(SO_3F)_4]# ion always has #(-1)# charge. The equivalent weight of #Br_2# in #[Br_3][Au(SO_3F)_4] + Br_2 -> [Br_5][Au(SO_3F)_4]# is?

A) 32
B) 80
C) 160
D) 400

1 Answer
Ernest Z.
Dec 4, 2017

The equivalent weight of #"Br"_2# in this reaction is D) 400 u.

Explanation:

The net ionic reaction is

#"Br"_3^"+" + "Br"_2 → "Br"_5^+#

The oxidation half-reaction is

#5"Br"_2 → 2"Br"_5^"+" + 2"e"^"-"#

The equivalent weight of a substance involved in a redox reaction is equal to its molecular weight divided by number of electrons lost or gained by one molecule of the substance.

Thus, we divide the half-reaction by 5 and get

#"Br"_2 → 2/5"Br"_5^"+" + 2/5"e"^"-"#

Then,

#"Eq. wt. of Br"_2 = "159.81 u"/(2/5) = "159.81 u" × 5/2 = "399.52 u"#

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