Chỉ giúp em bài 7 và 8 với ạ
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BT
2
DT
Đỗ Thanh Hải
CTVVIP
29 tháng 3 2021
IV
1 moon
2 when
3 for
4 from
5 living
6 understands
7 hungry
8 developes
VI
1 is written
2 is folded
3 is put
4 is sent
5 is collected
6 is sorted
7 is taken
8 is delivered
Giúp em bài 7 và bài 8 ik ạ
NL
Nguyễn Lê Phước Thịnh
CTVHS
28 tháng 2 2023
Bài 8:
Gọi số chưa biết là x
Theo đề, ta có: 0,75x+30%(0,75x)=19,5
=>x=20
NL
Nguyễn Lê Phước Thịnh
CTVHS
9 tháng 11 2025
a: ta có: \(5\cdot8^{12}\cdot9^5\cdot\left(-3\right)^2\cdot\left(-16\right)^5\)
\(=5\cdot\left(2^3\right)^{12}\cdot\left(3^2\right)^5\cdot3^2\cdot\left(-1\right)\cdot2^{20}\)
\(=-5\cdot3^{12}\cdot2^{56}\)
Ta có: \(7\cdot49^3\cdot81^5\cdot\left(-7\right)^{10}\cdot\left(-8\right)^5\)
\(=-7\cdot\left(7^2\right)^3\cdot\left(3^4\right)^5\cdot7^{10}\cdot\left(2^3\right)^5\)
\(=-7\cdot7^6\cdot3^{20}\cdot7^{10}\cdot2^{15}=-7^{17}\cdot2^{15}\cdot3^{20}\)
Ta có: \(B=\frac{5\cdot8^{12}\cdot9^5\cdot\left(-3\right)^2\cdot\left(-16\right)^5}{7\cdot49^3\cdot81^5\cdot\left(-7\right)^{10}\cdot\left(-8\right)^5}\)
\(=\frac{-5\cdot3^{12}\cdot2^{56}}{-7^{17}\cdot2^{15}\cdot3^{20}}=\frac{5\cdot2^{41}}{7^{17}\cdot3^8}\)
b: \(13\cdot4^7\cdot9^{15}-9^7\cdot\left(-16\right)^4\)
\(=13\cdot2^{14}\cdot3^{20}-3^{14}\cdot2^{16}\)
\(=3^{14}\cdot2^{14}\left(13\cdot3^6-2^2\right)\)
\(15\cdot3^{12}\cdot2^8+3\cdot27^5\cdot\left(-8\right)^{10}\)
\(=3\cdot5\cdot3^{12}\cdot2^8+3\cdot\left(3^3\right)^5\cdot\left(2^3\right)^{10}=3^{13}\cdot5\cdot2^8+3^{16}\cdot2^{30}\)
\(=3^{13}\cdot2^8\left(5+3^3\cdot2^{22}\right)\)
Ta có: \(C=\frac{13\cdot4^7\cdot9^{15}-9^7\cdot\left(-16\right)^4}{15\cdot3^{12}\cdot2^8+3\cdot27^5\cdot\left(-8\right)^{10}}\)
\(=\frac{3^{14}\cdot2^{14}\left(13\cdot3^6-2^2\right)}{3^{13}\cdot2^8\left(5+3^3\cdot2^{22}\right)}=\frac{3\cdot2^6\cdot\left(13\cdot3^6-2^2\right)}{5+3^3\cdot2^{22}}\)
BT
1
DT
Đỗ Thanh Hải
CTVVIP
27 tháng 4 2021
1 Facsimile was invented by Alexander Bain
2 Ha Long Bay was recognized as one of the world's seven wonders
3 Can garbage be used to make compost?
4 Romeo and Juliet was written by Shakespeare in 1592
5 Did the Wright brothers build the first plane in 1903?
6 Our factory doesn't produce this kine of paper
7 People have used ball point pens for many years
7 Whitcomb L.Judsin invented the zipper in 1893
BT
1
DT
Đỗ Thanh Hải
CTVVIP
17 tháng 4 2021
1 about - in
2 In - to
3 from - of - in
4 in - at - during
5 in - on
6 about
7 from
8 as
9 by - in - in
10 to - in
Bài 7:
Ta có: \(n_{Na_2O}=\dfrac{6,2}{62}=0,1\left(mol\right)\)
\(n_{H_2O}=\dfrac{73,8}{18}=4,1\left(mol\right)\)
PT: \(Na_2O+H_2O\rightarrow2NaOH\)
Xét tỉ lệ: \(\dfrac{0,1}{1}< \dfrac{4,1}{1}\), ta được H2O dư.
Theo PT: \(n_{NaOH}=2n_{Na_2O}=0,2\left(mol\right)\)
Ta có: m dd sau pư = mNa2O + mH2O = 6,2 + 73,8 = 80 (g)
\(\Rightarrow C\%_{NaOH}=\dfrac{0,2.40}{80}.100\%=10\%\)
Bạn tham khảo nhé!
Bài 8:
Ta có: \(n_{Zn}=\dfrac{6,5}{65}=0,1\left(mol\right)\)
PT: \(Zn+2HCl\rightarrow ZnCl_2+H_2\)
____0,1____0,2__________0,1 (mol)
a, VH2 = 0,1.22,4 = 2,24 (l)
b, \(C_{M_{HCl}}=\dfrac{0,2}{0,1}=2M\)
Bạn tham khảo nhé!