chem help...acids and bases

[purple.haze]

everytime i come across a question like the following, i never know what to do so if someone could show me the steps taken to find values it would be helpful..thanks

a 25.0 cm[sup]3[/sup] sample of 0.100 mol dm[sup]-3[/sup] hydrochloric acid was placed in a concial flask, and 0.100 mol dm[sup]-3[/sup] sodium hydroxide is added until a total of 50.0 cm[sup]3[/sup] had been added. Sketch a graph of pH against volume of NaOH(aq) added, clearly showing the volume of NaOH (aq) needed for complete reaction and the pH values at the start, the equivalence point and finish.

[~Lc~]

ok this is strong acid vs strong base graph, you can't really deduce tis graph, you should memorize it. I couldn't find a clear one online, but it's present in the IBID book... you'll just hve to deduce the pH values... which I've forgotten how to do sorry =(

[hellogoodbye]

[quote name='purple.haze' post='15620' date='Apr 27 2008, 03:22 AM']everytime i come across a question like the following, i never know what to do so if someone could show me the steps taken to find values it would be helpful..thanks

a 25.0 cm[sup]3[/sup] sample of 0.100 mol dm[sup]-3[/sup] hydrochloric acid was placed in a concial flask, and 0.100 mol dm[sup]-3[/sup] sodium hydroxide is added until a total of 50.0 cm[sup]3[/sup] had been added. Sketch a graph of pH against volume of NaOH(aq) added, clearly showing the volume of NaOH (aq) needed for complete reaction and the pH values at the start, the equivalence point and finish.[/quote]


im in sl so i didn't learn exactly how to sketch the graph, but i do know the basics.
the x axis is the moles or mL of titrant and the y axis is the pH, with 7 marked.
the equivalence point is the point when the grah hits a pH of 7
and for a low pH, the graph starts at a low ph and then rapidly increases, and then plateaus at the top.
its just the opposite for a high pH.
if this doesn't really make sense feel free to ask

[booji]

[quote name='hellogoodbye' post='17607' date='Jun 1 2008, 06:56 PM']im in sl so i didn't learn exactly how to sketch the graph, but i do know the basics.
the x axis is the moles or mL of titrant and the y axis is the pH, with 7 marked.
the equivalence point is the point when the grah hits a pH of 7
and for a low pH, the graph starts at a low ph and then rapidly increases, and then plateaus at the top.
its just the opposite for a high pH.
if this doesn't really make sense feel free to ask [/quote]

I am attaching two figures to this post. The second shows the titration curve/acid-base curve for the interaction of a strong acid with a strong base and vice versa. Note that the equivalence point always occurs at paH = 7 (due to neutralization effects). The first figure shows the titration curve for a weak acid vs. strong base. Note here the buffer region and that the equivalence point does not occur at pH = 7.

Edited June 16, 2008 by booji