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jeffy January 5th, 2010 03:20

Why are group I hydrides alkalis?
 
Okay until yesterday I thought hydrogen could only make H+ ions but now I know it can make H- ions also. I know that H+ is acid but why is H- alkali?

Gary Clark January 5th, 2010 07:53

Quote:

Originally Posted by jeffy (Post 2482)
Okay until yesterday I thought hydrogen could only make H+ ions but now I know it can make H- ions also. I know that H+ is acid but why is H- alkali?

When a metal hydride hits water, you get MH + H2O ---> MOH + H2 and the metal hydroxide is an alkali.

You could think of it as the hydride ion taking a hydrogen ion from the water to leave behind the OH-, which causes the alkalinity.

H- + H2O ---> H2 + OH-


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