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junior college 1 | H2 Maths
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Hi! Can someone please help me with (a)?
I got from -6 in CH3CH2OH to -1 in CH3CHO but the answer given is -1 to +1.. but i cant get it.. Thank u so much:)
Date Posted: 4 years ago
Views: 363
Oxidation state of O is taken to be -2 (except peroxides, superoxides, molecular oxygen or ozone)
Oxidation state of H is taken to be +1 (except hydrides or molecular hydrogen)
Surrounding the underlined C are one C, two Hs and one O.
The two Hs have a total O.S of +2.
The neighbouring C has the same electronegativity as the underlined C so they don't have to balance each other.
(This neighbouring C has an O.S of -3 to balance the 3 Hs bonded to it)
The O has a O.S of -2, and its neighbouring H has +1. Overall, -OH has an OS of -1.
Overall O.S surrounding the underlined carbon is +2 - 1 = +1
To balance that, the underlined carbon must have an O.S of -1.
Oxidation state of H is taken to be +1 (except hydrides or molecular hydrogen)
Surrounding the underlined C are one C, two Hs and one O.
The two Hs have a total O.S of +2.
The neighbouring C has the same electronegativity as the underlined C so they don't have to balance each other.
(This neighbouring C has an O.S of -3 to balance the 3 Hs bonded to it)
The O has a O.S of -2, and its neighbouring H has +1. Overall, -OH has an OS of -1.
Overall O.S surrounding the underlined carbon is +2 - 1 = +1
To balance that, the underlined carbon must have an O.S of -1.
In CH3CHO,
The underlined C is bonded to a O, the same neighbouring C and a H.
The H has O.S of +1
The O has O.S of -2
Overall : -1
To balance that, the underlined C must have an O.S of +1
The underlined C is bonded to a O, the same neighbouring C and a H.
The H has O.S of +1
The O has O.S of -2
Overall : -1
To balance that, the underlined C must have an O.S of +1
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Take a look at the rules written in red. Those dictate how to calculate the oxidation state of carbon in an organic compound.
In CH3CH2OH, the underlined Carbon is attached to O single bond and 2H single bond and a C single bond. Given that C bonded to C doesnt change ON, we can ignore it. Next the two H decreases the ON of C by 1 each, while O single bond increases it by 1. Hence -2 +1 = -1
For CH3CHO, the underlined Carbon is attached to C single bond, one O double bond and 1 H single bond. The H single bond decreases ON by 1 while the O double bond increases it by 2. Thus -1 +2 = +1
In CH3CH2OH, the underlined Carbon is attached to O single bond and 2H single bond and a C single bond. Given that C bonded to C doesnt change ON, we can ignore it. Next the two H decreases the ON of C by 1 each, while O single bond increases it by 1. Hence -2 +1 = -1
For CH3CHO, the underlined Carbon is attached to C single bond, one O double bond and 1 H single bond. The H single bond decreases ON by 1 while the O double bond increases it by 2. Thus -1 +2 = +1
Date Posted:
4 years ago
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