Question

Classify the following into lewis acids and lewis bases:
(a) ${H_2}O$
(b) $N{H_3}$
(c) ${H^ + }$
(d) $B{F_3}$
(e) $Al{H_3}$
(f) $ROH$
(g) $C{H_3}N{H_2}$
(h) $C{N^ - }$
(i) $^ + C{H_3}$
Lewis acids: (c), (d), (e), (i)
Lewis bases: (a), (b), (f), (g), (h)
If true enter $1$, else enter $0$.

Answer 1

Lewis acid may be defined as those substances which can accept an electron pair and lewis base is defined as that substance which can donate an electron pair. Species which have an extra pair of electrons can act as Lewis bases.

Complete step by step answer:
In this question, we have to find lewis acids and lewis bases among given species. Lewis acids are the species which can gain electron pairs and Lewis bases are the species which can donate electron pairs. Species which will have excess electrons can act as lewis bases.
${H_2}O$ is water. In water oxygen has a lone pair. This means a water molecule can donate a pair of electrons and hence it is a lewis base.
$N{H_3}$ is ammonia. ${H^ + }$ is hydrogen ion. Reaction between ammonia and hydrogen ion is as follows,
$N{H_3} + {H^ + }\xrightarrow[{}]{}NH_4^ +$
In this reaction, nitrogen donates its electron pair to hydrogen to make a bond. Nitrogen atoms of ammonia donate electron pairs, this means ammonia is lewis bases and hydrogen ions accept that electron pair. This means hydrogen ion is lewis acid.
$B{F_3}$ is boron trifluoride. This species is an electron deficient species, meaning this compound does not have enough electrons. So, this species can accept a pair of electrons and hence it is a lewis acid.
$Al{H_3}$ is aluminium hydride. $Al{H_3}$ can accept a pair of electrons as it is an electron deficient species and it has a vacant orbital also. So, it is a lewis acid.
$ROH$ is an organic compound. This is alcohol. $ROH$ contains oxygen which has an extra pair of electrons. This means $ROH$ can act as lewis bases.
$C{H_3}N{H_2}$ is methylamine. It is an organic compound. It contains a nitrogen atom, which has an extra pair of electrons. This means $C{H_3}N{H_2}$ is a lewis base (as it can donate electron pairs).
$C{N^ - }$ is cyanide also known as cyano group. As we can see that this species has negative charge this means free electrons are also present in this species. So, it can act as Lewis bases.
$^ + C{H_3}$ is methylium cation. This action exists in a gaseous phase. Positive charge on this species indicated that it can gain electrons. So, it is a lewis acid.
Among the given species, lewis acids are, ${H^ + }$ (c), $B{F_3}$ (d), $Al{H_3}$(e), $^ + C{H_3}$ (i) and lewis bases are, ${H_2}O$ (a), $N{H_3}$ (b), $ROH$ (f), $C{H_3}N{H_2}$ (g), $C{N^ - }$ (h).
This is the same as the statement given in the question and if the statement is correct we have to enter $1$ else $0$.
Given statement is correct. So, enter $1$.

Note:
Sometimes you can identify lewis acid or bases even from the formula of species. If the species has positive charge then it means it is electron deficient and hence is lewis acid and if the species has negative charge or an atom that has lone pair this means that species has excess electrons. So, that species will act as Lewis bases.