nếu là đề thi thì tự làm
các thầy cô báo k dc giúp r

Bài 11:

a) Số mol phân tử khí O2:

 \(n_{O2}=\dfrac{3,01.10^{24}}{6,02.10^{23}}=5\left(mol\right)\)

b) Khối lượng khí O2 là:

\(m_{O2}=32.5=160\left(g\right)\)

c) Thể tích khí O2 ở đktc:

\(V_{O2\left(đktc\right)}=5.22,4=112\left(l\right)\)

Bài 9:

nO2= 48/32=1,5(mol)

a) PTHH: C + O2 -to-> CO2

Ta có: nC=nCO2=nO2=1,5(mol)

=>mC=1,5.12=18(g)

b)  PTHH: S+ O2 -to-> SO2

Ta có: nS= nSO2=nO2= 1,5(mol)

=>mS=1,5.32=48(g)

c) PTHH: 4 P + 5 O2 -to-> 2 P2O5

Ta có: nP= 4/5. nO2= 4/5. 1,5=1,2(mol)

=>mP= 1,2.31=37,2(g)

TA CÓ:

\(\sqrt{x-1-4\sqrt{x-1}+4}+\sqrt{x-1+6\sqrt{x-1}+9}=5\)

\(\Leftrightarrow\sqrt{\left(\sqrt{x-1}-2\right)^2}+\sqrt{\left(\sqrt{x-1}-3\right)^2}=5\)

\(\Leftrightarrow\sqrt{x-1}-2+\sqrt{x-1}-3=5\Leftrightarrow2\sqrt{x-1}=10\Leftrightarrow\sqrt{x-1}=5\)

\(\Leftrightarrow x-1=25\Leftrightarrow x=26\)

ĐKXĐ: \(x\ge1\)

PT (=) \(\sqrt{\left(\sqrt{x-1}-2\right)^2}+\sqrt{\left(\sqrt{x-1}+3\right)^2}=5\) 

     (=) \(\sqrt{x-1}-2+\sqrt{x-1}+3=5\) (=)  \(2\sqrt{x-1}=4\)(=) \(\sqrt{x-1}=2\)(=) X = 5 (nhận)

\(5\cdot7\cdot77-7\cdot60+49\cdot25-15\cdot42\)

\(=5\cdot7\cdot77-7\cdot5\cdot12+7\cdot7\cdot5\cdot5-3\cdot5\cdot7\cdot6\)

\(=5\cdot7\left(77-12+5\cdot7-3\cdot6\right)\)

\(=35\cdot82=2\cdot5\cdot7\cdot41=10\cdot287=2870\)

không tính nhanh được :V

\(100^3-99^1+1\)

\(=100^3-\left(100-1\right)^3+1\)

\(=100^3-\left[100^3-3.100^2+3.100-1\right]+1\)

\(=3.100^2-3.100+2\)

\(=29702\)

Bài 3:

a: (2x+1,4)(3x-1,5)=0

=>\(\left[\begin{array}{l}2x+1,4=0\\ 3x-1,5=0\end{array}\right.\Rightarrow\left[\begin{array}{l}2x=-1,4\\ 3x=1,5\end{array}\right.\Rightarrow\left[\begin{array}{l}x=-0,7\\ x=0,5\end{array}\right.\)

b: \(\frac{2x}{3}-\frac16x-\frac{x+4}{2}=0\)

=>\(\frac{4x}{6}-\frac{x}{6}-\frac{3\left(x+4\right)}{6}=0\)

=>3x-3(x+4)=0

=>x-(x+4)=0

=>-4=0(vô lý)

c: \(\frac{x+3}{5}=-\frac32\)

=>\(x+3=-\frac32\cdot5=-\frac{15}{2}\)

=>\(x=-\frac{15}{2}-3=-\frac{21}{2}\)

d: \(\frac{1-5x}{2}=\frac{13}{36}-\frac{x+1}{3}\)

=>18(1-5x)=13-12(x+1)

=>18-90x=13-12x-12

=>-90x+18=-12x+1

=>-78x=-17

=>\(x=\frac{17}{78}\)

Bài 2:

a: \(A=\left|\frac{1}{-5}\right|-\frac{\left(-2\right)^2}{\left|-5\right|}-\frac{\left|-2\right|}{5}\)

\(=\frac15-\frac45-\frac25=\frac{1-6}{5}=-\frac55=-1\)

b: \(2^3+3\cdot\left(\frac19\right)^0-\frac{1}{2^2}\cdot4+\left\lbrack\left(-2\right)^2:\frac12\right\rbrack\cdot8\)

\(=8+3-\frac14\cdot4+4\cdot2\cdot8\)

=11-1+64

=10+64

=74

c: \(C=\left(-\frac23\right)^3:\left(-\frac23\right)^2+\frac{2^{40}\cdot3^{29}}{8^{13}\cdot9^{15}}\)

\(=-\frac23+\frac{2^{40}\cdot3^{29}}{2^{39}\cdot3^{30}}=-\frac23+\frac23=0\)