Đáp án:

Giải thích các bước giải:

Em tham khảo nha :

\(\begin{array}{l}
18)\\
a)\\
{M_X} = 2{M_O} = 2 \times 16 = 32\\
 \Rightarrow X:\text{Lưu huỳnh}(S)\\
b)\\
{M_Y} = 0,5{M_{Mg}} = 0,5 \times 24 = 12dvC\\
 \Rightarrow Y:Cacbon(C)\\
c)\\
{M_Z} = {M_{Na}} + 17 = 23 + 17 = 40dvC\\
 \Rightarrow Z:Canxi(Ca)\\
19)\\
a)\\
{m_C} = 1,9926 \times {10^{ - 23}}g\\
{M_C} = 12dvC\\
 \Rightarrow 1dvC = \dfrac{{1,9926 \times {{10}^{ - 23}}}}{{12}} = 1,6605 \times {10^{ - 24}}g\\
b)\\
{M_O} = 16dvC\\
 \Rightarrow {m_O} = 16 \times 1,6605 \times {10^{ - 24}} = 2,6568 \times {10^{ - 23}}g\\
{M_{Fe}} = 56dvC\\
 \Rightarrow {m_{Fe}} = 56 \times 1,6605 \times {10^{ - 24}} = 9,2988 \times {10^{ - 23}}g\\
{M_{Na}} = 23dvC\\
 \Rightarrow {m_{Na}} = 23 \times 1,6605 \times {10^{ - 24}}3,81915 \times {10^{ - 23}}g
\end{array}\)