In organic chemistry we use lots of non-aqueous very strong bases... and formally, the pKa of NaOH as a proton acid is around 35 or 40. This pretty much never applies in practice unless you were to mix water with, say, methyl sodium (very dangerous!!); both protons would be removed from water to give sodium oxide.
But we also talk about pKa values with respect to bases, so from that viewpoint, the pKa of NaOH (as in the pKa of its conjugate acid) is 15.7.
In organic chemistry we use lots of non-aqueous very strong bases... and formally, the pKa of NaOH as a proton acid is around 35 or 40. This pretty much never applies in practice unless you were to mix water with, say, methyl sodium (very dangerous!!); both protons would be removed from water to give sodium oxide.
But we also talk about pKa values with respect to bases, so from that viewpoint, the pKa of NaOH (as in the pKa of its conjugate acid) is 15.7.
It's an interesting question. When you ask what the pKa of NaOH is, are you viewing NaOH as an acid or a base? The two views yield two different pKa values.When NaOH is viewed as an acid, its conjugate base is [math]O^{-2}[/math]. Much more usual is when NaOH is viewed as a base, it acts like [math]OH^-[/math] and its conjugate acid is [math]H_2O[/math]. pKa value is a measure of acidity (a stands for acid), namely, the ability of a compound to give out its hydrogen in the form of [math]H_3O^+[/math] ion, according to the concept of Bronsted acids. pKa can also be a measure of the basicity of a conjugate base. For instance, the same pKa value determines the acidity of [math]H_2O[/math] and the basicity of [math]OH^-[/math].
The pKa of [math]H_3O^+[/math] viewed as an acid is 0 (or 1.7 depending on convention), which means that [math]H_3O^+[/math] is a standard of acidity; that of [math]H_2O[/math], again as an acid, is 14 (or 15.7). It's in a reverse scale, meaning that the higher the pKa value the lower the acidity. For every notch higher, the acidity drops ten times. So [math]H_3O^+[/math] is 100 trillion times stronger acid than[math] H_2O[/math]. NaOH is a strong base. If NaOH is viewed as an acid, its acidity has got to be at least 100 trillion times weaker than that of [math]H_2O,[/math] which tells the pKa of NaOH as an acid is at least 28~38. The weakest acid I have seen in textbooks is ethane with a whopping pKa 62. A pKa 62 seems absurd, but all it means is that ethane has a very strong conjugate base, [math]C_2H_5^-[/math]. [math]C_2H_5^-[/math] is much much much stronger than NaOH as a base.
If NaOH is viewed as a base, its pKa is an ordinary 14 or 15.7.
It's an interesting question. When you ask what the pKa of NaOH is, are you viewing NaOH as an acid or a base? The two views yield two different pKa values.When NaOH is viewed as an acid, its conjugate base is [math]O^{-2}[/math]. Much more usual is when NaOH is viewed as a base, it acts like [math]OH^-[/math] and its conjugate acid is [math]H_2O[/math]. pKa value is a measure of acidity (a stands for acid), namely, the ability of a compound to give out its hydrogen in the form of [math]H_3O^+[/math] ion, according to the concept of Bronsted acids. pKa can also be a measure of the basicity of a conjugate base. For instance, the same pKa value determines the acidity of [math]H_2O[/math] and the basicity of [math]OH^-[/math].
The pKa of [math]H_3O^+[/math] viewed as an acid is 0 (or 1.7 depending on convention), which means that [math]H_3O^+[/math] is a standard of acidity; that of [math]H_2O[/math], again as an acid, is 14 (or 15.7). It's in a reverse scale, meaning that the higher the pKa value the lower the acidity. For every notch higher, the acidity drops ten times. So [math]H_3O^+[/math] is 100 trillion times stronger acid than[math] H_2O[/math]. NaOH is a strong base. If NaOH is viewed as an acid, its acidity has got to be at least 100 trillion times weaker than that of [math]H_2O,[/math] which tells the pKa of NaOH as an acid is at least 28~38. The weakest acid I have seen in textbooks is ethane with a whopping pKa 62. A pKa 62 seems absurd, but all it means is that ethane has a very strong conjugate base, [math]C_2H_5^-[/math]. [math]C_2H_5^-[/math] is much much much stronger than NaOH as a base.
If NaOH is viewed as a base, its pKa is an ordinary 14 or 15.7.
In organic chemistry we use lots of non-aqueous very strong bases... and formally, the pKa of NaOH as a proton acid is around 35 or 40. This pretty much never applies in practice unless you were to mix water with, say, methyl sodium (very dangerous!!); both protons would be removed from water to give sodium oxide.
But we also talk about pKa values with respect to bases, so from that viewpoint, the pKa of NaOH (as in the pKa of its conjugate acid) is 15.7.
In organic chemistry we use lots of non-aqueous very strong bases... and formally, the pKa of NaOH as a proton acid is around 35 or 40. This pretty much never applies in practice unless you were to mix water with, say, methyl sodium (very dangerous!!); both protons would be removed from water to give sodium oxide.
But we also talk about pKa values with respect to bases, so from that viewpoint, the pKa of NaOH (as in the pKa of its conjugate acid) is 15.7.
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It's an interesting question. When you ask what the pKa of NaOH is, are you viewing NaOH as an acid or a base? The two views yield two different pKa values.When NaOH is viewed as an acid, its conjugate base is [math]O^{-2}[/math]. Much more usual is when NaOH is viewed as a base, it acts like [math]OH^-[/math] and its conjugate acid is [math]H_2O[/math]. pKa value is a measure of acidity (a stands for acid), namely, the ability of a compound to give out its hydrogen in the form of [math]H_3O^+[/math] ion, according to the concept of Bronsted acids. pKa can also be a measure of the basicity of a conjugate base. For instance, the same pKa value determines the acidity of [math]H_2O[/math] and the basicity of [math]OH^-[/math].
The pKa of [math]H_3O^+[/math] viewed as an acid is 0 (or 1.7 depending on convention), which means that [math]H_3O^+[/math] is a standard of acidity; that of [math]H_2O[/math], again as an acid, is 14 (or 15.7). It's in a reverse scale, meaning that the higher the pKa value the lower the acidity. For every notch higher, the acidity drops ten times. So [math]H_3O^+[/math] is 100 trillion times stronger acid than[math] H_2O[/math]. NaOH is a strong base. If NaOH is viewed as an acid, its acidity has got to be at least 100 trillion times weaker than that of [math]H_2O,[/math] which tells the pKa of NaOH as an acid is at least 28~38. The weakest acid I have seen in textbooks is ethane with a whopping pKa 62. A pKa 62 seems absurd, but all it means is that ethane has a very strong conjugate base, [math]C_2H_5^-[/math]. [math]C_2H_5^-[/math] is much much much stronger than NaOH as a base.
If NaOH is viewed as a base, its pKa is an ordinary 14 or 15.7.
Overwhelming? I thought so.
It's an interesting question. When you ask what the pKa of NaOH is, are you viewing NaOH as an acid or a base? The two views yield two different pKa values.When NaOH is viewed as an acid, its conjugate base is [math]O^{-2}[/math]. Much more usual is when NaOH is viewed as a base, it acts like [math]OH^-[/math] and its conjugate acid is [math]H_2O[/math]. pKa value is a measure of acidity (a stands for acid), namely, the ability of a compound to give out its hydrogen in the form of [math]H_3O^+[/math] ion, according to the concept of Bronsted acids. pKa can also be a measure of the basicity of a conjugate base. For instance, the same pKa value determines the acidity of [math]H_2O[/math] and the basicity of [math]OH^-[/math].
The pKa of [math]H_3O^+[/math] viewed as an acid is 0 (or 1.7 depending on convention), which means that [math]H_3O^+[/math] is a standard of acidity; that of [math]H_2O[/math], again as an acid, is 14 (or 15.7). It's in a reverse scale, meaning that the higher the pKa value the lower the acidity. For every notch higher, the acidity drops ten times. So [math]H_3O^+[/math] is 100 trillion times stronger acid than[math] H_2O[/math]. NaOH is a strong base. If NaOH is viewed as an acid, its acidity has got to be at least 100 trillion times weaker than that of [math]H_2O,[/math] which tells the pKa of NaOH as an acid is at least 28~38. The weakest acid I have seen in textbooks is ethane with a whopping pKa 62. A pKa 62 seems absurd, but all it means is that ethane has a very strong conjugate base, [math]C_2H_5^-[/math]. [math]C_2H_5^-[/math] is much much much stronger than NaOH as a base.
If NaOH is viewed as a base, its pKa is an ordinary 14 or 15.7.
Overwhelming? I thought so.
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