PTHH: KOH + HNO₃ \(\rightarrow\) KNO₃ + H₂O

Theo pt: 0,056 .. 0,063 .... 0,101 ............. (kg)

Theo đề: ...? ........ ? ......... 1000 .............. (kg)

Đổi: 1 tấn = 1000kg

56g = 0,056kg

63g = 0,063kg

101g = 0,101kg

\(m_{KOH}=\dfrac{1000.0,056}{0,101}\approx554,46\left(kg\right)\)

\(m_{HNO_3}=\dfrac{1000.0,063}{0,101}\approx623,76\left(kg\right)\)

Tìm các số x, y, z biết:

a) \(\dfrac{x-1}{2}=\dfrac{y-2}{3}=\dfrac{z-3}{4}\) và \(x+y+z=49\)

Áp dụng tính chất dãy tỉ số bằng nhau, ta có:

\(\dfrac{x-1}{2}=\dfrac{y-2}{3}=\dfrac{z-3}{4}=\dfrac{x-1+y-2+z-3}{2+3+4}=\dfrac{49-6}{9}=\dfrac{43}{9}\)

\(\Rightarrow\left\{{}\begin{matrix}\dfrac{x-1}{2}=\dfrac{43}{9}\\\dfrac{y-2}{3}=\dfrac{43}{9}\\\dfrac{z-3}{4}=\dfrac{43}{9}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x-1=\dfrac{86}{9}\\y-2=\dfrac{43}{3}\\z-3=\dfrac{172}{9}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{95}{9}\\y=\dfrac{49}{3}\\z=\dfrac{199}{9}\end{matrix}\right.\)

Vậy \(x=\dfrac{95}{9};y=\dfrac{49}{3};z=\dfrac{199}{9}\)

b) \(\dfrac{2x}{3}=\dfrac{3y}{4}=\dfrac{4z}{5}\) và \(x+y+z=49\)

Đặt \(\dfrac{2x}{3}=\dfrac{3y}{4}=\dfrac{4z}{5}=k\left(k\ne0\right)\)

\(\Rightarrow\left\{{}\begin{matrix}2x=3k\\3y=4k\\4z=5k\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{3k}{2}\\y=\dfrac{4k}{3}\\z=\dfrac{5k}{4}\end{matrix}\right.\)

Theo giả thiết ta có: \(x+y+z=49\)

\(\Leftrightarrow\dfrac{3k}{2}+\dfrac{4k}{3}+\dfrac{5k}{4}=49\)

\(\Leftrightarrow\dfrac{18k+16k+15k}{12}=\dfrac{588}{12}\)

\(\Leftrightarrow18k+16k+15k=588\)

\(\Leftrightarrow49k=588\)

\(\Leftrightarrow k=12\)

\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{3.12}{2}=18\\y=\dfrac{4.12}{3}=16\\z=\dfrac{5.12}{4}=15\end{matrix}\right.\)

Vậy \(x=18;y=16;z=15\)

Từ các tỉ số sau đây có lập được tỉ lệ thức không?

a) \(\dfrac{2}{5}:4\) và \(\dfrac{4}{5}:8\)

Ta có: \(\dfrac{2}{5}:4=\dfrac{2}{5}.\dfrac{1}{4}=\dfrac{2}{20}=\dfrac{1}{10}\)

\(\dfrac{4}{5}:8=\dfrac{4}{5}.\dfrac{1}{8}=\dfrac{4}{40}=\dfrac{1}{10}\)

Vậy ta lập được tỉ lệ thức \(\dfrac{2}{20}=\dfrac{4}{40}\left(=\dfrac{1}{10}\right)\)

b) \(-\dfrac{31}{2}:7\) và \(-\dfrac{22}{5}:\dfrac{71}{5}\)

Ta có: \(-\dfrac{31}{2}:7=-\dfrac{31}{2}.\dfrac{1}{7}=-\dfrac{31}{14}\)

\(-\dfrac{22}{5}:\dfrac{71}{5}=-\dfrac{22}{5}.\dfrac{5}{71}=-\dfrac{22}{71}\)

Vậy ta không lập được tỉ lệ thức vì \(-\dfrac{31}{14}\ne-\dfrac{22}{71}\)

Viết các PTHH theo chuỗi phản ứng.

\(\left(1\right)Fe_2O_3+3H_2\rightarrow2Fe+3H_2O\)

\(\left(2\right)Fe+2HCl\rightarrow FeCl_2+H_2\uparrow\)

\(\left(3\right)FeCl_2+Ba\left(OH\right)_2\rightarrow Fe\left(OH\right)_2\downarrow+BaCl_2\)

\(\left(4\right)Fe\left(OH\right)_2+H_2SO_4\rightarrow FeSO_4+2H_2O\)

\(\left(5\right)2Fe+3Cl_2\rightarrow2FeCl_3\)

\(\left(6\right)FeCl_3+3NaOH\rightarrow Fe\left(OH\right)_3\downarrow+3NaCl\)

\(\left(7\right)2Fe\left(OH\right)_3\underrightarrow{t^o}Fe_2O_3+3H_2O\)

Sử dụng thế giới trong ngoặc để kết hợp mỗi cặp câu

The coffee is very strong. I can't drink it. (too...to)

=> The coffee is too strong for me to drink.

Nêu hiện tượng xảy ra và viết phương trình hóa học (nếu có) khi

a) Thả kim loại Na vào dd CuSO₄ : Ban đầu Na sẽ tan dần trong nước và xuất hiện sủa bọt khí do khí hiđro được giải phóng, sau đó NaOH mới sinh ra tiếp tục phản ứng với CuSO₄ có trong dung dịch tạo kết tủa Cu(OH)₂ màu xanh không tan trong nước.

2Na + 2H₂O \(\rightarrow\) 2NaOH + H₂\(\uparrow\)

2NaOH + CuSO₄ \(\rightarrow\) Na₂SO₄ + Cu(OH)₂\(\downarrow\)

b) Nhúng chiếc đinh sắt vào dd CuSO₄ : Một phần đinh sắt bị hòa tan, kim loại đồng bám ngoài đinh sắt và màu xanh lam của dung dịch ban đầu nhạt dần.
Fe + CuSO₄ \(\rightarrow\) FeSO₄ + Cu

c) Sục từ từ đến dư dd HCl vào dd NaAlO₂ : Ban đầu, thấy kết tủa keo trắng tạo thành tăng dần đến cực đại, sau đó lại bị hòa tan dần tới hết sinh ra dung dịch trong suốt.
NaAlO₂ + HCl + H₂O \(\rightarrow\) Al(OH)₃\(\downarrow\) + NaCl
Al(OH)₃ + 3HCl \(\rightarrow\) AlCl₃ + 3H₂O

Câu 1:

Ta có ^PTKBa(NO₃)₂ ^{= PTK}Ba ^{+ 2PTK}NO3

Mà ^PTKBa(NO₃)₂ ^{= 261} và ^PTKBa ^{= 137} nên

^2PTKNO₃ ^{= 261 - 137 = 124}

^{=> PTK}NO₃^{= 124 : 2 = 62 (đvC)}

1. He said to me "You should take a few days off."

=> He told me (that) I should take a few days off.

=> He advised me to take a few days off.

2. Her teacher said to her "You should improve your pronunciation."

=> Her teacher told her (that) she should improve her pronunciation.

=> Her teacher advised her to improve her pronunciation.

3. She said to me "You ought to keep your body warm".

=> She told me (that) I ought to keep my body warm.

=> She advised me to keep my body warm.

4. My teacher said to me "You shouldn't go to school late".

=> My teacher told me (that) I shouldn't go to school late.

=> My teacher advised me not to go to school late.

5. He said to me "You had better not stay up late".

=> He told me (that) I had better not stay up late.

=> He advised me not to stay up late.

Phân tích đa thức thành nhân tử

\(3a-3b+a^2-2ab+b^2=\)

\(=\left(3a-3b\right)+\left(a^2-2ab+b^2\right)\)

\(=3\left(a-b\right)+\left(a-b\right)^2\)

\(=3\left(a-b\right)+\left(a-b\right)\left(a-b\right)\)

\(=\left(a-b\right)\left(3+a-b\right)\)

1. I would like you to help me put the chair away.

=> Do you mind putting the chair away for me?

2. Vinh keeps forgetting his homework.

=> Vinh is always forgetting his homework.

3. Keeping the environment clean is very important.

=> It’s very important to keep the environment clean.

4. Old car tires are recycled to make shoes and sandals.

=> People recycled old car tires to make shoes and sandals.

5. It’s three years since I last spoke to her.

=> I haven’t spoken to her for three years.

6. Tam doesn’t type as fast as she used to.

=> Tam used to type fast.

7. How long is it since you used the car?

=> When did you start to use/ using the car?

8. We started living here 15 years ago.

=> We have lived here for 15 years.

9. Let’s meet inside the center, at the cafe corner.

=> How about meeting inside the center, at the cafe corner?

10. I’ve never eaten this kind of cake.

=> It’s the first time I have eaten this kind of cake.

11. The film was so interesting that we watched it several times.

=> It was such an interesting film that we watched it several times.

12. Write your name here

=> Let your name be written here.

13. People think that computer games are harmful.

=> It is thought that computer games are harmful.

14. We couldn’t drive fast because of the fog.

=> The fog prevented us from driving.

15. It is a pity she can’t speak French fluently.

=> She wishes she could speak French fluently.