a, \(\dfrac{-18}{31}< \dfrac{15}{-37}\)

b, \(\dfrac{-23}{91}< \dfrac{131}{-535}\)

c, \(\dfrac{-72}{73}< \dfrac{-58}{99}\)

\(\dfrac{m_{ct}.100\%}{49}=20\%\Rightarrow m_{ct}=9,8\left(g\right)\)

\(n_{H_2SO_4}=\dfrac{9,8}{98}=0,1\left(mol\right)\)

\(Zn+H_2SO_4\rightarrow ZnSO_4+H_2\)

----------0,1-----------------------0,1 (mol)

\(V_{H_2}=0,1.22,4=2,24\left(l\right)\)

B

\(2x+6x+6=\)0

\(\Leftrightarrow8x=-6\\ \Leftrightarrow x=\dfrac{-3}{4}\)

\(\dfrac{m_{ct}.100\%}{100}=24,5\%\Rightarrow m_{ct}=24,5\left(g\right)\)

\(n_{H_2SO_4}=\dfrac{24,5}{98}=0,25\left(mol\right)\)

\(Ba\left(OH\right)_2+H_2SO_4\rightarrow BaSO_4+2H_2O\)

------------------0,25---------0,25-------------

\(m_{BaSO_4}=233.0,25=58,52\left(g\right)\)

bạn tải ảnh lên nhé chứ coppy paste không được đâu

D

5-0+3 =8

55 nha

4B 5C