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Do all bases release OH-? Do all bases have the ability to receive an H+ ion? As an example, CaCO3 is a base but it doesn't release OH- ions.

PS. I am a high school student

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    $\begingroup$ What definition of acidity are you using? There are more than one. $\endgroup$ Commented Feb 5, 2023 at 9:01
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    $\begingroup$ Depends on what solvent they are in. $\endgroup$
    – Waylander
    Commented Feb 5, 2023 at 10:18
  • $\begingroup$ $\ce{CaCO3}$ can react with acids, but it is not a base $\endgroup$
    – Maurice
    Commented Feb 5, 2023 at 10:28
  • $\begingroup$ Be aware that laconic, not elaborated questions without hints of solving attempt are usually frown upon and often closed on the StackExchange network. OTOH, well elaborated questions have higher probability to receive acceptable answers. How do I ask a good question?. $\endgroup$
    – Poutnik
    Commented Feb 5, 2023 at 11:12
  • $\begingroup$ @Maurice CaCO3 is an Usanovich base, providing negative anion for the reaction. $\endgroup$
    – Poutnik
    Commented Feb 5, 2023 at 11:52

3 Answers 3

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Not all bases directly release $\ce{OH-}$ ion, but in case of water solutions, their chemical interactions lead finally to increasing of $\ce{OH-}$ concentration.

It was originally thought all bases are hydroxides, releasing hydroxide ion.(Arrhenius)

It was later realized not only hydroxides cause alkalinity, so acids and bases were redefined in sense of proton ($\ce{H+(aq)}$ in water) exchange (Brønsted-Lowry, B-L). It is not limited to water solvent nor even to liquids, being applicable to solids or gases as well.

$$\ce{NH3 + H2O <=> NH4+ + OH-}$$ $$\ce{CO3^2- + H2O <=> HCO3- + OH-}$$

So ammonia does not release hydroxide ion, but captures proton from water. $\ce{CaCO3(s)}$ either releases carbonate anion that is a B-L base, or is able to capture $\ce{H+}$ itself. Similarly for solid $\ce{NaOH}$.

$$\ce{CaCO3(s) + 2 H+(aq) -> Ca^2+(aq) + CO2(g) + H2O(l)}$$

This should be enough for you for now, the rest is left for optional further reading.


There are several developed theories of acids and bases, each being more general and involving older ones.

Bases by the Arrhenius acid-base theory release $\ce{OH-}$ ion. Like solid $\ce{NaOH}$ when dissolved.

Bases by the Brønsted-Lowry acid-base theory capture a proton like $\ce{NH3}$ or $\ce{OH-}$ or $\ce{H2O}$ or $\ce{CO3^2-}$. It is applicable for all gaseous, solid and liquid phases, not limited to water solutions.

Bases by the Lewis acid-base theory donate an electron pair, like in prior paragraph, or $\ce{NH3}$ reacting with $\ce{BF}$ (a Lewis acid, accepting an electron pair). This remove the prior limitation to the proton exchange.

enter image description here

(image credit to Wikimedia Commons User Riptide360).

There are therefore often used terms "Arrhenius base", "Brønsted-Lowry base", "Lewis base".


There are even more general and complex acid-base theories in the link above, but that would be out of the needed knowledge scope

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No, NH3 is a base. NH3 contains no oxygen - no hydroxide ions - so it cannot release hydroxide ions when dissolved in aqueous solution. I think you are getting the terms alkali and base mixed up - all alkalis contain hydroxide ions - they release them in aqueous solution - so all alkalis are bases but not all bases are alkalis.

Do all bases have the ability to receive H+ ions? Yes - the definition of a base is

a substance that can accept hydrogen ions in water and can neutralize an acid

So all bases have the ability to receive hydrogen cations (H+ ions) - or "protons" as some chemists call them - you may have heard the term "acid donates a proton" - that's speak for H+ ions leaving the dissolved acid compound and joining onto a base as part of a neutralisation reaction (acid + base --> salt - plus H2O if the base is an alkali OR plus H2O + CO2 if base is a carbonate).

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There are TWO general types of chemical reactions. Those involving electron pairs or bonds, the electron pairs change their positions in or between molecules, are Acid-Base reactions. The base furnishes the electron pair the acid accepts it. It can be a subtle interaction or a brute force reaction between a strong acid and strong base in water. This means that a myriad of explanations has been presented to try to describe every nuance. Ignore them and learn Chemistry and the mechanisms for reactions. Acidity and basicity depend on the reaction.

The second general class of reactions involves the actual transfer of electrons usually one at a time. These are known as oxidation-reduction or REDOX reactions. The two usually happen together but can be separated. Unfortunately, these also have a wide range of explanations but usually involve neutral atoms, metals, and elements of differing electronegativity. A further complication is that, with imagination, an acid-base reaction can be written or thought of as a redox reaction and vice-versa.

The solution is to learn the definitions to pass the test, but to look into the overall reactions to try to understand more about what is going on and not be bound to restrictive definitions.

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