Просклонять слова столь , дерево , гроза , снег по падежам

Что это за вещества? 
N2SO4, CaO, MgCl2 

Complete the sentences, use a(an), the or zero article. 1)We knew he was ... foreigner because he spoke with a strange accent. 2)There was ... old Lady of France who taught ... little ducklings to dance. 3) He has not worked hard so thee is not much hope that he will pass ... exam. 4) .;.. hotel is ... place where ... students of ... travellers can get ... meals and ... rooms. 5) "Never lend... books, for no one ever returns them; ... only books I have in my library are ... books that other people have lent me." 6) I had like .. glass of water. 7) Who is ... boy standing by ... piano? 8) Today is ... last day when we can give them ... papers. 9) What ... thick dictionaries! 10) The browns have got ... boy and ... girl. ... girl is three years older than ... boy.