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IgorLugansk [536]
3 years ago
10

Một hỗn hợp X gồm CH3OH; C2H5OH; phenol có khối lượng 28,9 gam phản ứng vừa hết với 100ml dung dịch NaOH 2M. Phần trăm theo khối

lượng phenol là ? Biết C = 12; O = 16; H = 1; Na = 23. *
Chemistry
1 answer:
slavikrds [6]3 years ago
3 0

Answer:

nNaOH = 0,2 mol

Trong hỗn hợp các chất đề bài cho chỉ có phenol tác dụng với NaOH

C6H5OH + NaOH → C6H5ONa + H2O

   0,2  ←     0,2 (mol)

⟹ mphenol = 0,2.94 = 18,8 gam

⟹  

%mC6H5OH=18,8/28,9 x100%= 65,05%

Explanation:

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The half life of 226/88 Ra is 1620 years. How much of a 12 g sample of 226/88 Ra will be left after 8 half lives?
Aloiza [94]

Answer:

0.0468 g.

Explanation:

  • The decay of radioactive elements obeys first-order kinetics.
  • For a first-order reaction: k = ln2/(t1/2) = 0.693/(t1/2).

Where, k is the rate constant of the reaction.

t1/2 is the half-life time of the reaction (t1/2 = 1620 years).

∴ k = ln2/(t1/2) = 0.693/(1620 years) = 4.28 x 10⁻⁴ year⁻¹.

  • For first-order reaction: <em>kt = lna/(a-x).</em>

where, k is the rate constant of the reaction (k = 4.28 x 10⁻⁴ year⁻¹).

t is the time of the reaction (t = t1/2 x 8 = 1620 years x 8 = 12960 year).

a is the initial concentration (a = 12.0 g).

(a-x) is the remaining concentration.

∴ kt = lna/(a-x)

(4.28 x 10⁻⁴ year⁻¹)(12960 year) = ln(12)/(a-x).

5.54688 = ln(12)/(a-x).

Taking e for the both sides:

256.34 = (12)/(a-x).

<em>∴ (a-x) = 12/256.34 = 0.0468 g.</em>

8 0
3 years ago
How many milliliters of C5H8 can be made from 366 mL C5H12 ?
zlopas [31]

The number of Ml  of C₅H₈  that can  be  made  from 366  ml  C₅H₁₂  is 314.7 ml  of C₅H₈


  <u><em>calculation</em></u>

 step  1: write  the  equation for  formation of C₅H₈

C₅H₁₂  →  C₅H₈  + 2 H₂

Step 2: find the mass of C₅H₁₂

mass = density × volume

= 0.620 g/ml × 366 ml =226.92 g

Step 3: find moles  Of  C₅H₁₂

moles  = mass÷  molar mass

from periodic table the  molar mass of  C₅H₁₂ = (12 x5) +(  1 x12) = 72 g/mol

moles = 226.92 g÷ 72 g/mol =3.152 moles

Step 4: use the  mole ratio  to determine the  moles of C₅H₈

C₅H₁₂:C₅H₈  is 1:1  from equation above

Therefore the  moles of C₅H₈  is also = 3.152  moles

Step 5: find the mass  of C₅H₈

mass = moles x molar mass

from periodic table the  molar mass of C₅H₈ = (12 x5) +( 1 x8) = 68 g/mol

= 3.152  moles x 68 g/mol = 214.34 g

Step 6: find Ml of  C₅H₈

=mass / density

= 214.34 g/0.681 g/ml = 314.7 ml



8 0
3 years ago
The particle picture is best described as...
mixas84 [53]

Answer:

Both are pure substances and a compound

8 0
3 years ago
Although Rutherford is credited with the famous gold foil scattering experiment, he didn’t actually conduct this experiment hims
DerKrebs [107]
If he was the primary scientist doing it as he did alot of the heavy lifting then yes its ok, but i also think how the others should also me at least mentioned. Or they could just not name the experiment by a person just so its not too biased
3 0
3 years ago
The electromagnetic force acts between what
spayn [35]

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3 0
3 years ago
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