a) \(E=\dfrac{U}{d}=\dfrac{12}{0,2}=60\)V/s

b) \(A=qEd=2\cdot10^{-6}\cdot12=2,4\cdot10^{-5}\)J

C

Có m_{rắn tăng}=m+12,8-m=12,8\(\Rightarrow\)\(m_O=12,8\Rightarrow n_{O^{2-}}=n_O=0,4mol\)

          \(2H^+\)    +     \(O^{2-}\)     \(\rightarrow\)    \(H_2O\)

           0,8     \(\leftarrow\)     0,4

  \(n_{HNO_3}=n_{H^+}=0,8mol\)\(\Rightarrow V_{HNO_3}=\dfrac{0,8}{2}=0,4l=400ml\)

\(n_X=\dfrac{1,12}{22,4}=0,05\Rightarrow\dfrac{n_{HNO_3}}{n_X}=\dfrac{0,6}{0,05}=12\Rightarrow\)X là N₂

_{(sản phẩm khử duy nhất nên không xuất hiện \(NH_4^+\)})

\(\underrightarrow{BTe:}\) \(3n_{Al}=10n_{N_2}\Rightarrow n_{Al}=\dfrac{1}{6}\Rightarrow m_{Al}=4,5g\)

1. My friend has a sense of humor.

2, I am made to study hard by my parents.

3, I spend 2 hours doing my homework.

ĐK:  \(sinx\ne0\Rightarrow x\ne m\pi\). Pt\(\Rightarrow\left[{}\begin{matrix}cotx=0\\cotx-1=0\end{matrix}\right.\)

    \(\Rightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{2}+k\pi\\x=\dfrac{\pi}{4}+k\pi\end{matrix}\right.\)(tmđk)

a)\(E_H=E_A+E_B=k\dfrac{\left|q_1\right|}{AH^2}+k\dfrac{\left|q_2\right|}{BH^2}=1440\)V/m

b)Có BM-AM=AB\(\Rightarrow M\in AB\) và nằm ngoài đoạn AB.

   \(E_M=\left|E_B-E_A\right|\)=71920V/m

ĐK:\(cosx\ne0\Rightarrow x\ne\dfrac{\pi}{2}+m\pi\)

Pt: \(sinx\cdot\dfrac{1}{cos^2x}+\dfrac{sin^2x}{cos^2x}=1\)

     \(\Rightarrow sinx+sin^2x=cos^2x\)

     \(\Rightarrow sinx+sin^2x=1-sin^2x\Rightarrow2sin^2x+sinx-1=0\)

     \(\Rightarrow\left[{}\begin{matrix}sinx=\dfrac{1}{2}\\sinx=-1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{6}+k2\pi\\x=\dfrac{5}{6}\pi+k2\pi\\x=-\dfrac{\pi}{2}+k2\pi\end{matrix}\right.\)

Đối chiếu đk của x ta đc hai họ nghiệm \(\left[{}\begin{matrix}x=\dfrac{\pi}{6}+k2\pi\\x=\dfrac{5\pi}{6}+k2\pi\end{matrix}\right.\)