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3 years ago

20. The mass of one mole of lead (Pb) atoms is 207.2 g. Use a proportion to calculate the n

Chemistry

1 answer:

AnnZ [28]3 years ago

8 0

Answer:

a) atoms Pb = 4.3595 E22 amu

b) g = ( 6.022 E23 amu ) × ( Mw )

Explanation:

m Pb = 207.2 g / mol Pb

sample:

∴ m = 15.00 g

a) atoms Pb = ?

1 mol ≡ 6.022 E23 amu

⇒ atoms Pb = (15.00g Pb)(mol Pb/207.2 g)(6.022 E23 amu/mol)

⇒ atoms Pb = 4.3595 E22 amu

b) relationship:

∴ 1 mol (n) ≡ 6.022 E23 amu......(1)

∴ mass (g) ≡ (Mw)×(n)

⇒ n = g / Mw..........(2)

∴ Mw: molecular weight

(1) = (2):

⇒ g / Mw ≡ 6.022 E23 amu

⇒ g ≡ ( 6.022 E23 amu ) × ( Mw )

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The decomposition of dinitrogen pentoxide, N2O5, to NO2 and O2 is a first-order reaction. At 60°C, the rate constant is 2.8 × 10

Ugo [173]

Answer:

The correct option is a.

Explanation:

$2N_2O_5\rightarrow 4NO_2 + O_2$

125 kPa

125kpa - 2x 4x x

Total pressure after reaction = 176 kPa

125 kPa - 2x + 4x + x = 176 kPa

x = 17

125 kpa - 2x = 125 kPa - 2(17) = 91 kPa

Initial pressure of the dinitrogen pentoxide ,(at t=0) = $P_o= 125 kPa$

Final pressure of the dinitrogen pentoxide, (at t = t) = P = 91 kPa

The rate constant is = $k = 2.8\times 10^{-3} min^{-1}$

$t=\frac{2.303}{k}\log\frac{P_o}{P}$

$t=\frac{2.303}{2.8\times 10^{-3} min^{-1}}\log\frac{125 kPa}{91 kPa}$

$t=113.3969 minutes\approx 113 minutes$

It will take 113 minutes for the total pressure to reach 176 kPa.

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2 years ago

Calculate the oxidation number for carbon in CH4

Maksim231197 [3]

Answer:

Explanation:

Oxidation number of neutral compound is 0

Oxidation number of hydrogen in methane is -1

C + (-1×4) = 0

C - 4 = 0

C = 4

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2 years ago

Molarity of 0.50 mol sugar in 270 mL of solution.

EastWind [94]

<h3>Answer:</h3>

1.85 M

<h3>Explanation:</h3>

We are given;

Number of moles as 0.50 mol
Volume of the solution is 270 ml

But, 1000 mL = 1 L

Thus, volume of the solution is 0.27 L

We are required to calculate the molarity of the solution;

Molarity refers to the concentration of a solution in moles per liter.
It is calculated by dividing number of moles with the volume.

Molarity = Moles ÷ Volume

In this case;

Molarity = 0.50 moles ÷ 0.27 L

= 1.85 Mol/L or 1.85 M

Therefore, molarity of the solution is 1.85 M

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2 years ago

Fill in the blanks using terms from this unit.

kolbaska11 [484]

Answer:

See the answer below

Explanation:

Even though plants are rooted in the ground, they still move, exert force, and do work.

Plant cells have very strong cell walls that allow pressure to build up inside of the cell as water is absorbed. This pressure is called turgor.

When turgor pressure is high enough in a cell, the cell walls become firm and as a result, the cell becomes rigid and the plant is able to stand tall and straight.

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When the wilted plant gets enough water, the cells will become rigid again, and the plant will stand firm and straight once again.

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2 years ago

Read 2 more answers

(4) Calculate the % of a compound that can be removed from liquid phase 1 by using ONE to FOUR extractions with a liquid phase 2

maksim [4K]

Answer:

One extraction: 50%

Two extractions: 75%

Three extractions: 87.5%

Four extractions: 93.75%

Explanation:

The following equation relates the fraction q of the compound left in volume V₁ of phase 1 that is extracted n times with volume V₂.

qⁿ = (V₁/(V₁ + KV₂))ⁿ

We also know that V₂ = 1/2(V₁) and K = 2, so these expressions can be substituted into the above equation:

qⁿ = (V₁/(V₁ + 2(1/2V₁))ⁿ = (V₁/(V₁ + V₁))ⁿ = (V₁/(2V₁))ⁿ = (1/2)ⁿ

When n = 1, q = 1/2, so the fraction removed from phase 1 is also 1/2, or 50%.

When n = 2, q = (1/2)² = 1/4, so the fraction removed from phase 1 is (1 - 1/4) = 3/4 or 75%.

When n = 3, q = (1/2)³ = 1/8, so the fraction removed from phase 1 is (1 - 1/8) = 7/8 or 87.5%.

When n = 4, q = (1/2)⁴ = 1/16, so the fraction removed from phase 1 is (1 - 1/16) = 15/16 or 93.75%.

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3 years ago