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

         Herman Melville, an American author best known today for his novel Moby Dick, was actually more popular during his lifetime for some of his other works. He traveled extensively and used the knowledge gained during his travels as the basis for his early novels. In 1837, at the age of eighteen, Melville signed as a cabin boy on a merchant ship that was to sail from his Massachusetts home to Liverpool, England. His experiences on this trip served as a basis for the novel Redburn (1849). In 1841 Melville set out on a whaling ship headed for the South Seas. After jumping ship in Tahiti, he wandered around the islands of Tahiti and Moorea. This South Sea island sojourn was a backdrop to the novel Omoo (1847). After three years away from home, Melville joined up with a U.S. naval frigate that was returning to the eastern United States around Cape Horn. The novel White-Jacket (1850) describes this lengthy voyage as a navy seaman. 

         With the publication of these early adventure novels, Melville developed a strong and loyal following among readers eager for his tales of exotic places and situations. However, in 1851, with the publication of Moby Dick, Melville's popularity started to diminish. Moby Dick, on one level the saga of the hunt for the great white whale, was also a heavily symbolic allegory of the heroic struggle of man against the universe. The public was not ready for Melville's literary metamorphosis from romantic adventure to philosophical symbolism. It is ironic that the novel that served to diminish Melville's popularity during his lifetime is the one for which he is best known today.

The main subject of the passage is_________.

A. Melville’s travels

B. Moby Dick

C. Melville’s personal background

D. the popularity of Melville’s novels

mấy dạng này bạn dùng quỳ tím để nhận biết nhé

Ba(OH)2 lmf quỳ tím chuyển màu thành xanh

HCl làm quỳ tím chuyển màu thành đỏ

NaNO3 ko làm quỳ tím chuyển màu

dùng quỳ tím ẩm để nhận biết nhé

chất làm quỳ tím chuyển màu thành xanh=> NaOH

chất làm quỳ tím chuyển màu thành đỏ=>H₂SO₄

\(C\%=\dfrac{S}{S+100}.100\)

từ CT trên ta tính được \(S_{10^0C}=18g\)

ở 10⁰C

18gam KNO3 tan trong 100g H2O-->118 gam dung dịch bão hòa

x gam KNO3 tan trong y gam H2O-->236gam dd bão hòa

=> x=36 và y=200

gọi a là khối lượng KNO3 cần thêm vào

\(S_{20^oC}=30=\dfrac{m_{ct}.100}{m_{H2O}}=\dfrac{\left(36+a\right).100}{200+a}\)

giải ra ta có a=34,286

ý dưới làm tương tự

CTTQ liên hệ giữa độ tan ( S ) và nồng độ phần trăm ( C% )

\(C\%=\dfrac{S}{S+100}.100\)

a) C% dd bão hòa CuSO₄ ở nhiệt độ t₁:

\(C\%=\dfrac{20}{20+100}.100=16,67\%\)

b)

ở t₂ độ C

34,2g CuSO4+100g H2O--->134,2gam dd bão hòa

x(g) CuSO₄+ y ( g) H₂O---->134,2gam dd bão hòa

=> x=34,2 và y=100

ở t₁ độ C

20g CuSO₄+100g H₂O-->dd bão hòa

z(g) CuSO₄+100g H2O--> dd bão hòa

=> Z=20

=> có 34,2-20=14,2g CuSO₄ tách ra

\(CuSO_4+5H_2O->CuSO_4.5H_2O\)

n_CuSO4=14,2/160=0,08875mol

=> n_CuSO4.5H2O=0,08875mol=>m_tinh-thể=0,08875.250=22,1875gam