Modelová Otázka ID 2857 - 
Jakou změnu vyvolá přídavek hydroxidu sodného k roztoku slabé kyseliny HA?
Správná odpověď je: A
Slabé kyseliny se v roztoku nachází částečně disociované na ionty H+ a A−, částečně v nedisociované formě HA. Pokud k roztoku přidáme NaOH, dojde k disociaci NaOH na Na+ a OH−. Na+ ionty rovnováhu neovlivňují. OH− ionty reagují s H+ ionty, proto se koncentrace H+ v roztoku snižuje. Systém se snaží znovu nastolit rovnováhu – disociuje se více molekul kyseliny, aby se zvýšil počet H+ iontů. Proto klesá počet nedisociovaných molekul kyseliny a stoupá počet iontů A−.
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