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the nomenclature of hydrogen bonding can be a little bit confusing so let's work through this problem to bring a little more clarity to the situation so let's start by defining hydrogen bond donors and acceptors every hydrogen bond includes two components a polarized X H bond in which the hydrogen end is the positive end and the X or hetero atom end is the negative end and a second hetero atom that has a lone pair which is partially negatively charged the hydrogen bond itself is the interaction between the positively charged hydrogen atom at least partially positive and the partially negative X hetero atom even though the black hetero atom is donating electron density towards the hydrogen this is referred to as the hydrogen bond acceptor in a sense because it's accepting the X H covalent bond from the blue portion meanwhile the XH bond or the molecule containing the X H bond is known as the hydrogen bond donor so we see that in order for a molecule to act as a hydrogen bond donor it must have this X H bond and in the vast majority of cases molecules that contain X H bonds also contain lone pairs on the hetero atom and so these can also act as acceptors so that's not a universal requirement for X H bonds hydrogen-bond acceptors must contain a hetero atom barring a lone pair and there are many cases many of which we'll see in these examples where a molecule can serve as a hydrogen bond acceptor but not as a hydrogen bond donor because all of its hetero atoms are bonded to either other hetero atoms or to carbon so let's go through each of these molecules and determine whether each can act as a hydrogen bond acceptor or hydrogen bond donor so in the case of a we see a nitrogen atom this nitrogen has a lone pair on it and so it can certainly act as a hydrogen bond acceptor however it does not include any nitrogen hydrogen and so it cannot act as a hydrogen bond donor molecule B has an oxygen which bears lone pairs and so it like a can act as an acceptor and it also includes an O age bond and so it can act as a hydrogen bond donor as well molecule C includes two hetero atoms two oxygens each of which has two lone pairs and so C can like a and B act as a hydrogen bond acceptor however like a the hetero atoms in C are not bonded to hydrogen's and so this molecule cannot act as a hydrogen bond donor molecule D is hydrogen fluoride and the fluorine has three lone pairs on it and so this molecule can act as a hydrogen bond acceptor it also includes an H ex bond here the hetero atom is fluorine and so this can act as a hydrogen bond donor as well now if we look at molecule II molecule II includes no hetero atoms and as a result it can neither serve as a hydrogen bond donor or a hydrogen bond acceptor so this will not participate in hydrogen bonding at all molecule F has an oxygen atom with two lone pairs and so can serve as a hydrogen bond acceptor but again a lot like molecule a the oxygen is not bonded to any hydrogen's and so this can't serve as a hydrogen bond donor molecule G includes a carbonyl oxygen again with two lone pairs we're seeing this pattern over and over again and so this can act as a hydrogen bond acceptor it can engage in a hydrogen bond with XH on something else but it doesn't include any oxygen hydrogen bonds itself and so it cannot serve as a hydrogen bond donor molecule h includes two oxygen atoms as part of a carboxylic acid and one of those is bonded to a hydrogen so molecule h can serve both as a hydrogen bond acceptor and a hydrogen bond donor molecule i includes no hetero atoms and so a lot like kc this molecule cannot engage in hydrogen bonding at all molecule j includes a nitrogen with one own pair and so it can serve as a hydrogen bond acceptor it also includes nitrogen hydrogen bonds which can act as hydrogen bond donors so molecule J needs to go on our list of hydrogen bond donors molecule K includes two hetero atoms and oxygen and a nitrogen however neither of these is bonded to a hydrogen atom and so while molecule K can act as a hydrogen bond acceptor it cannot act as a hydrogen bond donor and finally molecule L includes the central oxygen atom with two lone pairs but that oxygen is bonded to two phenyl rings and includes no bonds to hydrogen and so molecule L can act as a hydrogen bond acceptor but not a hydrogen bond donor so hopefully running quickly through these examples has shown you that as long as we can identify lone pairs and XH bonds within molecules it's fairly straightforward to identify molecules that can hydrogen bond and can serve as either hydrogen-bond acceptors with lone pairs or hydrogen bond donors with XH bonds