7)
a) Ở 20 độ C 36 gam muối ăn tan trong 100 gam nước tạo 136 gam dung dịch bão hòa.
\( \to C{\% _{NaCl}} = \frac{{36}}{{136}} = 26,47\% \)
b) \({m_{{H_2}S{O_4}}} = 150.14\% = 21{\text{ gam}}\)
8)
a) \(2Al + 3C{l_2}\xrightarrow{{}}2AlC{L_3}\)
b) \(Ca{(OH)_2} + 2HCl\xrightarrow{{}}CaC{l_2} + 2{H_2}O\)
c) \(3Fe + 2{O_2}\xrightarrow{{{t^o}}}F{e_3}{O_4}\)
d) \(2Al + 6HCl\xrightarrow{{}}2AlC{l_3} + 3{H_2}\)
e) \(A{l_2}{O_3} + 3{H_2}S{O_4}\xrightarrow{{}}A{l_2}{(S{O_4})_3} + 3{H_2}O\)