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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: onyxboltz on March 12, 2019, 09:08:12 AM

Title: Need help with some VSEPR q's..
Post by: onyxboltz on March 12, 2019, 09:08:12 AM
so some verification for:
formic acid molecule, CHOOH, (image attached for CHOOH check it out)
1.What is the parent geometry and molecular geometry about the carbon atom and about the hydroxyl oxygen atom?
I put for carbon, parent and molecular trigonal planar. for hydrxyl oxygen i put Tetrahedral for parent and bent for molecular.

2. I now have a formate ion; CHOO- (image attached for CHOO- check it out, picture in RED)
What is the bond order for O...C...O, would it just be 2..?

3. Last but not least... Dimethyl hydrazine, (CH3)2N-NH2, is a liquid at room temperature. How many atoms in this molecule have tetrahedral parent geometry?   
I got 2 from sketching it and identifying.

just need verification if these are the correct answers
cheers :)
Title: Re: Need help with some VSEPR q's..
Post by: chenbeier on March 12, 2019, 10:05:21 AM
The carbon and Oxygen in the C=O group has sp² hybridisation. So its trigonal planar. The O in the OH group is sp³ hybridisation and its tetrahedral.
The formiat anion looks ok.

The Dimethylhydrazine has two methyl groups which are tetrahedral and also the two nitrogen are sp³ hybridisisized, what means they also tetrahedral.
Title: Re: Need help with some VSEPR q's..
Post by: onyxboltz on March 12, 2019, 11:33:22 PM
The carbon and Oxygen in the C=O group has sp² hybridisation. So its trigonal planar. The O in the OH group is sp³ hybridisation and its tetrahedral.
The formiat anion looks ok.

The Dimethylhydrazine has two methyl groups which are tetrahedral and also the two nitrogen are sp³ hybridisisized, what means they also tetrahedral.

wouldn’t it be 2 in total since nitrogen only has 3 side group bonds?

Cheers
Title: Re: Need help with some VSEPR q's..
Post by: chenbeier on March 13, 2019, 05:49:42 AM
Nitrogen has 3 bonds and one electron pair, so its tetrahedral, you also described oxygen in Hydroxyl as tetrahedral. Here wie have two bonds and 2 electron pairs. The same in halogen compounds, only one bond and 3 electronpairs.
Title: Re: Need help with some VSEPR q's..
Post by: mjc123 on March 14, 2019, 09:39:31 AM
The bond order in formate ion is not 2. Does it have two double bonds?
Hint: fractional bond orders are permissible.