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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: matt123 on November 08, 2010, 09:36:07 am

Title: WEAKER ACID? HIGHER KA? OR LOWER?
Post by: matt123 on November 08, 2010, 09:36:07 am: hey guys
if an acid is WEAKER .. will it have a smaller or higher KA than a stronger acid?
Title: Re: WEAKER ACID? HIGHER KA? OR LOWER?
Post by: samiira on November 08, 2010, 09:45:30 am: the weaker the acid, the smaller the ka
Title: Re: WEAKER ACID? HIGHER KA? OR LOWER?
Post by: m@tty on November 08, 2010, 01:02:07 pm: One way to view this is that because $K_a \varpropto K$ and remembering that a higher value of $K$ indicates that the reaction occurs to a greater extent. Similarly a smaller $K$ , or $K_a$ , value means that the yield at equilibrium is lower.

So just apply the same rules that you normally do for the equilibrium constant.

Or from a more conceptual stance, remember that $K_a=\frac{[H^+][A^-]}{[HA]}$ products are on top, so a bigger $K_a$ value indicates a higher proportion of ionisation.. And, again, a lower $K_a$ is indicative of a weaker acid.
Title: Re: WEAKER ACID? HIGHER KA? OR LOWER?
Post by: matt123 on November 08, 2010, 02:44:13 pm: Quote from: m@tty on November 08, 2010, 01:02:07 pm
One way to view this is that because $K_a \varpropto K$ and remembering that a higher value of $K$ indicates that the reaction occurs to a greater extent. Similarly a smaller $K$ , or $K_a$ , value means that the yield at equilibrium is lower.

So just apply the same rules that you normally do for the equilibrium constant.

Or from a more conceptual stance, remember that $K_a=\frac{[H^+][A^-]}{[HA]}$ products are on top, so a bigger $K_a$ value indicates a higher proportion of ionisation.. And, again, a lower $K_a$ is indicative of a weaker acid.

Cheers mate.