Đề yêu cầu?

Ta có: \(1000kg/m^3=1kg/l\)

\(\Rightarrow m=V.D=1.1=1\left(kg\right)\)

\(n_{Fe}=\dfrac{11,2}{56}=0,2\left(mol\right)\)

\(PTHH:Fe+2HCl\rightarrow FeCl_2+H_2\)

(mol)____0,2____0,4____0,2____0,2__

\(a.m_{FeCl_2}=0,2.127=25,4\left(g\right)\)

\(b.C\%_{ddFeCl_2}=\dfrac{m_{ct}}{m_{ddspu}}.100=\dfrac{25,4}{11,2+120-0,2.2}.100=19,4\left(\%\right)\)

\(c.C\%_{ddHCl}=\dfrac{36,5.0,4}{120}.100=12,17\left(\%\right)\)

Câu a sử dụng pp thế

Câu b thì đặt \(\left\{{}\begin{matrix}u=\dfrac{1}{x}\\v=\dfrac{1}{y}\end{matrix}\right.\) ra được hệ mới, giải tìm u,v rồi tìm x,y

Ta có: \(p=mv\)

\(\Rightarrow p'=mv'=3mv=3p\)

Polluted air can directly do harm to people's health

Lan sings more beautifully than her sister

\(a.f\left(1\right)=f\left(-1\right)\Leftrightarrow a+b+c=a-b+c\Leftrightarrow2b=0\Leftrightarrow b=0\)

\(\Rightarrow f\left(x\right)=ax^2+c\)

Khi đó ta có:

\(\left\{{}\begin{matrix}f\left(m\right)=am^2+c\\f\left(-m\right)=am^2+c\end{matrix}\right.\Rightarrow f\left(m\right)=f\left(-m\right)\forall m\)

The workers built a bridge in our neighborhood last month

→ A bridge was built in our neighborhood by the workers last month