Question

1. Quantos mols de moléculas há em 2,3g de H2O?

2. Quantas moléculas de CH4 há em 2,0 gramas da substância?

Answer 1

$\large\boxed{\begin{array}{l}\rm 1)\\\sf 1~mol~de~mol\acute eculas\longrightarrow18~g\\\sf x\longrightarrow 2,3~g\\\sf 18x=2,3\\\sf x=\dfrac{2,3}{18}\\\\\sf x=0,12~mols~de~mol\acute eculas \end{array}}$

$\boxed{\begin{array}{l}\sf 16~g~de~CH_4\longrightarrow 6,02\cdot10^{23}~mol\acute eculas\\\sf 2~g~de~CH_4\longrightarrow x\\\sf 16x=2\cdot6,02\cdot10^{23}\\\sf x=\dfrac{12,04\cdot10^{23}}{16}\\\\\sf x=0,7525\cdot10^{23}\\\sf x=7,525\cdot10^{22}~mol\acute eculas\end{array}}$