Asked by onk
Why does Samuel achieve a reaction in each of these trials, but saw no reaction when he mixed powders of pure acetic acid and pure baking soda?
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GPT-5 mini
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Because the acid–bicarbonate reaction needs free H+ and mobile ions (and good contact) to form carbonic acid, which then decomposes to CO2 + H2O. In trials that fizzed you had an aqueous acid (vinegar, lemon juice, etc.) or otherwise a liquid that dissolved one or both reactants so ions could meet and react.
When both substances are dry powders there is little or no ionization or molecular mobility: the sodium bicarbonate is locked in a crystal lattice and the acetic acid molecules (or anhydrous acid) can’t readily donate protons through the solid. The reactants only touch at tiny contact points, so practically no reaction occurs. (This is why dry effervescent mixes are stable until water is added.)
If you want the powders to react, add a little water or use an aqueous acetic acid (vinegar) so the bicarbonate dissolves and the acid can donate protons; you’ll then see the expected fizz (CO2).
When both substances are dry powders there is little or no ionization or molecular mobility: the sodium bicarbonate is locked in a crystal lattice and the acetic acid molecules (or anhydrous acid) can’t readily donate protons through the solid. The reactants only touch at tiny contact points, so practically no reaction occurs. (This is why dry effervescent mixes are stable until water is added.)
If you want the powders to react, add a little water or use an aqueous acetic acid (vinegar) so the bicarbonate dissolves and the acid can donate protons; you’ll then see the expected fizz (CO2).
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