CaCO₃
\(\%M_{\dfrac{Ca}{CaCO_3}}=\dfrac{40}{100}.100\%=40\%\)
\(\%M_{\dfrac{C}{CaCO_3}}=\dfrac{12}{100}.100\%=12\%\)
\(\%M_{\dfrac{O}{CaCO_3}}=100\%-\left(40\%+12\%\right)=48\%\)
H₂SO₄
\(\%M_{\dfrac{H_2}{H_2SO_4}}=\dfrac{2}{98}.100\%=2,04\%\)
\(\%M_{\dfrac{S}{H_2SO_4}}=\dfrac{32}{98}.100\%=32,65\%\)
\(\%M_{\dfrac{O}{H_2SO_4}}=100\%-\left(2,04\%+32,65\%\right)=65,31\%\)
Fe₂O3
\(\%M_{\dfrac{Fe}{Fe_2O_3}}=\dfrac{112}{160}.100\%=70\%\)
\(\%M_{\dfrac{O}{Fe_2O_3}}=100\%-70\%=30\%\)
 

a) \(n_{CO_2\left(đktc\right)}=\dfrac{6,72}{22,4}=0,3\left(mol\right)\)
\(m_{CO_2}=0,3.44=13,2\left(g\right)\)
\(n_{Cl_2}=\dfrac{1,344}{22,4}=0,06\left(mol\right)\)
\(m_{Cl_2}=0,06.71=4,26\left(g\right)\)
b)\(m_{Na_2O}=0,32.62=19,84\left(g\right)\)
\(m_{CaCO_3}=1,44.100=144\left(g\right)\)

Mẫu chung là 55 vậy -2 quy đồng lên là -2.11= -22 bạn.

\(\dfrac{-2}{5}-\dfrac{-3}{11}=\dfrac{-2}{5}+\dfrac{3}{11}=\dfrac{-22}{55}+\dfrac{15}{55}=\dfrac{-7}{55}\)

Gọi công thức tổng quát của oxit là : P_xO_y
\(M_{P_x}=\dfrac{31.x}{142}.100\%=43,66\% \Rightarrow x=2\)
\(M_{O_y}=\dfrac{16.y}{142}.100\%=\left(100\%-43,66\%\right) \Rightarrow y=5\)
Vậy công thức hóa học của oxit là : P₂O₅
\(\Rightarrow \) Chọn B

a) \(N=\dfrac{1}{2}.2.Z\Rightarrow Z=N=E=P\)
\(S=2Z+N=60\)
\(\rightarrow Z=N=P=E=20\)
b) Cấu hình e của R :
1s²2s²2p⁶3s²3p⁶4s²
Số e lớp ngoài cùng là 2 nên R là kim loại.

1. She does her homework every evening.
2. She isn't doing her homework at the moment.
3. I don't usually stay up late.
4. Lan always helps her mother do the housework.
5. How far is it from your house to the supermarket.
6. How does Miss Lien go to work.
7. Lan's new house is larger than her old house.
8.China is larger than Viet Nam.