Often, the 副助詞（ふくじょし） (adverbial particle) か
is used in the middle of a sentence, in the same way that it is as a 終助詞（しゅうじょし） (sentence ending particle). The main differences are as follows:
副助詞（ふくじょし） - Highlights 不確（ふたし）かであること ‘uncertain things’. This is the same か as in どこか
終助詞（しゅうじょし） - Highlights 疑問（ぎもん）や
質問（しつもん） ‘doubts and questions’. This is a direct question.
In the case of the adverbial particle か
and ‘uncertain things’, this will almost always be followed by a word that is seeking information about the uncertain thing.
Do you know if the CEO is coming to the end of year party? (Literally, ‘If the CEO is coming, do you know?’)
Do you know if this is enough? (Literally, ‘If this is enough, do you know?’)
Do you know why they are destroying this building? (Literally, ‘Why they are destroying it, do you know?’)
Do you know what time the festival is going to end? (Literally, ‘What time it will end, do you know?’)
As can be seen in these examples, sometimes the 副助詞（ふくじょし） will appear by itself, and sometimes it will appear together with the 終助詞（しゅうじょし） in the same sentence. However, due to the ‘uncertainty’ being displayed by the adverbial particle, the question marker at the end of the sentence is not required.
This か should not be preceded by だ (or です), this is why words like どこか and 誰（だれ）か are not どこだか and 誰（だれ）だか.