Câu 3:
Đặt \(M_R=x\left(g/mol\right)\)
Ta có \(n_R=\dfrac{78}{x}\left(mol\right);n_{RCl}=\dfrac{149}{x+35,5}\left(mol\right)\)
\(PTHH:2R+Cl_2\rightarrow2RCl\\ \Rightarrow n_R=n_{RCl}\\ \Rightarrow\dfrac{78}{x}=\dfrac{149}{x+35,5}\\ \Rightarrow78x+2769=149x\\ \Rightarrow71x=2769\\ \Rightarrow x=39\)
Vậy R là Kali(K)
Câu 2:
a) Na
b) Fe, Al, Mg, Na
Câu 1:
a)
\(n_{AgNO_3}=0,5.0,1=0,05\left(mol\right)\\ Fe+2AgNO_3\rightarrow Fe\left(NO_3\right)_2+2Ag\\ 0,025......0,05......0,025.....0,05\left(mol\right)\\ m=m_{rắn}=\left(15-0,025.56\right)+0,05.108=19\left(g\right)\)
b)
\(Fe\left(NO_3\right)_2+2NaOH\rightarrow Fe\left(OH\right)_2\downarrow+2NaNO_3\\ Fe\left(OH\right)_2\underrightarrow{^{to}}FeO+H_2O\\ n_{FeO}=n_{Fe\left(OH\right)_2}=n_{Fe\left(NO_3\right)_2}=0,025\left(mol\right)\\ m_{oxit}=m_r=m_{FeO}=72.0,025=1,8\left(g\right)\)