\(n_{KCl}=a\left(mol\right),n_{KBr}=b\left(mol\right)\)
Giả sử :
\(a+b=1\left(mol\right)\left(1\right)\)
\(KCl+AgNO_3\rightarrow KNO_3+AgCl\)
\(KBr+AgNO_3\rightarrow KNO_3+AgBr\)
\(m_{\downarrow}=143.5a+188b=170\left(a+b\right)\left(g\right)\)
\(\Leftrightarrow26.5a-18b=0\left(2\right)\)
\(\left(1\right),\left(2\right):a=\dfrac{36}{89},b=\dfrac{53}{89}\)
\(\%KCl=\dfrac{\dfrac{36}{89}\cdot74.5\cdot100\%}{\dfrac{36}{89}\cdot74.5+\dfrac{53}{89}\cdot119}=29.84\%\)