(1): 4Na + O₂ -> 2Na₂O

Na₂O + CO₂ → Na₂CO₃

Na₂CO₃ + Ba(OH)₂→ 2NaOH + BaCO₃

(2): Ca + \(\dfrac{1}{2}\)O₂→ CaO

CaO + H₂O→ Ca(OH)₂

Ca(OH)₂ + CO₂ → CaCO₃ +H₂O

CaCO₃ + H₂SO₄ → CaSO₄ +H₂O +CO₂

(3) : S + O₂ → SO₂

SO₂ + \(\dfrac{1}{2}\)O₂ → SO₃

SO₃ + H₂O → H₂SO₄

H₂SO₄ + K₂O → K₂SO₄ +H₂O

H₂O + SO₂ → H₂SO₃

(6):Cu + \(\dfrac{1}{2}\)O₂ → CuO

CuO + 2HCl → CuCl₂ + H₂O

CuCl₂ + 2NaOH → Cu(OH)₂ + NaCl
Cu(OH)_{2 →} CuO + H₂O

Một cửa hàng có 84 kg đường, đã bán được  34 kg trong số đường đó. Hỏi cửa hàng còn lại bao nhiêu ki-lô-gam đường?

Cho hình thoi ABCD có AB = BC = CD = DA = 4cm và B A C ^ = 60 0 . Diện tích của hình thoi ABCD là

A. 8  c m 2  

B.  8 3 c m 2  

C. 16  c m 2  

D. 15 c m 2  

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase for each of the blanks.

During the last 400 years, most scientists have (31)_______ on mathematics for the development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (32)_______ of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no education beyond reading and writing.

In 1812, Faraday was hired as a bottle washer by the great chemist Humphrey Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy’s life embittered (33)________ jealousy. Faraday made the first electric motor in 1821, a device that used electricity to produce movement. Then Faraday became interested in the relationship between electricity and magnetism. In 1831, he (34)_________ that when a magnet is moved near a wire, electricity flows in the wire. With this discovery, he produced a machine for making electricity called dynamo. Faraday then went on to show how electricity affects chemical substances.

Because Faraday believed that money should be given to the poor, when he grew old, he was very poor. However , Queen Victoria (35)________ him for his discoveries by giving him a stipend and a house. He died in 1867.

Question 31:

A. made

B. consisted

C. relied

D. insisted

Cho hàm số y = x 2 3 − x  . Mệnh đề nào sau đây là đúng?

A. Hàm số đã cho đồng biến trên khoảng  2 ; + ∞

B. Hàm số đã cho đồng biến trên khoảng  0 ; 2

C. Hàm số đã cho đồng biến trên khoảng  − ∞ ; 3

D. Hàm số đã cho đồng biến trên khoảng  − ∞ ; 0

Good lucky

Coi tàu đứng yên so với xe máy,vận tốc xe máy so với tàu là v1-v0

a) Thời gian để xe máy vượt qua tàu hỏa

t1= L/ v1-v0= 200/v1-15 (1)

Thời gian t1 đó xe máy đi được quãng đường s1=800m

t1 = s1/v1 = 800/v1 (2)

(1) (2) => 200/v1-15 = 800/ v1

=> v1= 20 m/s

b) Vận tốc của xe đạp so với tàu là v0 + v2

vận tốc của xe máy so với tàu là v1-v0

Khi xe máy gặp xe đạp, ta có: L- l/ v1-v0 = l /v2+ v0

200-160/20-15=160/ v2 +15

=> v2= 5 m/s

c) Chọn trục Ox cùng hướng cới hướng chuyển động của tàu, gốc o tại vị trí xe máy gặp tàu tại t0 = 0s

Thời gian để tàu qua xe đạp là t =\(\dfrac{L}{v2+v0}=\dfrac{200}{5+15}=10s\)

Khoảng cách giữa xe đạp và xe máy khi tàu qua xe đạp

d= |s1- s2|

=| v1t- (v2t + L)| = | (v1+v2)t -L | = | ( 20+ 5)*10 - 200| =50m

Mark the letter A, B, C, or D to indicate the word that differs from the other three in position the of the primary stress in each of the following questions.

A. convenient

B. permanent

C. attractive

D. important

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

Wolfgang Amadeus Mozart’s was the only-surviving son of Leopold and Maria Pertl Mozart. Leopold was a successful composer, violinist, and assistant concert master at the Salzburg court. Wolfgang's mother, a constantly ill housewife, was born to a middle class family of local community leaders. His only sister was Maria Anna. With their father’s encouragement and guidance, they both were introduced to music at an early age. Leopold started Anna on keyboard when she was seven, as three-year old Wolfgang looked on. Mimicking her playing, Wolfgang quickly began to show a strong understanding of chords, tonality, and tempo. Soon, he too was being tutored by his father.

Leopold was a devoted and task-oriented teacher to both his children. He made the lessons fun, but also insisted on a strong work ethic and perfection. Fortunately, both children excelled well in these areas. Recognising their special talents, Leopold devoted much of his time to their education in music as well as other subjects. Wolfgang soon showed signs of excelling beyond his father's teachings with an early composition at age five and demonstrating outstanding ability on harpsichord and the violin. He would soon go on to play the piano, organ and viola.

The word “devoted" in the passage is closest in meaning to ____.

A. inconstant

B. strict

C. committed

D. only

l i m x → + ∞ 3 x 4 - 2 x + 3 5 x 4 + 3 x + 1 bằng: 

A. 0

B. 4/9

C. 3/5

D. +∞