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Dafna1 [17]
3 years ago
15

The number of moles in 250 L of He gas at STP is ________ mol, Round to a whole number,

Chemistry
1 answer:
7nadin3 [17]3 years ago
7 0

Answer: The number of moles in 250.0 L of He at STP is 11.0 mole.

Explanation:

  • It is known that 1.0 mole of a gas at STP conditions will occupy 22.7 L.
  • To show this information: STP means that T = 0.0 °C = 273.15 K and P = 1.0 kPa =  (100/101.325) = 0.9869 atm.
  • From the ideal gas law: PV = nRT.
  • Where, P is the pressure in atm <em>(P = 1.0 atm at STP).</em>
  • V is the volume in L.
  • n is the number of moles (n = 1.0 mole).
  • R is the general gas constant (R = 0.0821 L.atm/mol.K).
  • T is the temperature in K (T = 273.15 K at STP).
  • and now we can get the volume of 1.0 mole at STP: V = nRT/P
  • V = (1.0 mole x 0.0821 L.atm/mol.K x 273.15 K) / (0.9869 atm) = 22.7 L.
  • Now, we can get the number of moles of 250.0 L of He at STP:

<em>Using cross multiplication:</em>

1.0 mole → 22.7 L

??? mole → 250.0 L

  • The number of moles in 250.0 L of He at STP = (250.0 L x 1.0 mole) / (22.7 L) = 11.01 mole ≅ 11.0 mole.
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g100num [7]
<h3>Answer:</h3>

Lead-205 (Pb-205)

<h3>Explanation:</h3>

<u>We are given;</u>

  • An atom of Po-209

We are supposed to identify its product after an alpha decay;

  • Polonium-209 has a mass number of 209 and an atomic number of 84.
  • When an element undergoes an alpha decay, the mass number decreases by 4 while the atomic number decreases by 2.
  • Therefore, when Po-209 undergoes alpha decay it results to the formation of a product with a mass number of 205 and atomic number of 82.
  • The product from this decay is Pb-205, because Pb-205 has a mass number of 205 and atomic number 82.
  • The equation for the decay is;

²⁰⁹₈₄Po → ²⁰⁵₈₂Pb + ⁴₂He

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7 0
3 years ago
10.
Andru [333]

Answer: 1.8 moles Fe and 2.7 moles CO_2 are produced.

Explanation:

The balanced chemical reaction is:

Fe_2O_3+3CO\rightarrow 2Fe+3CO_2  

According to stoichiometry :

3 moles of CO require 1 mole of Fe_2O_3

Thus 2.7 moles of CO will require=\frac{1}{3}\times 2.7=0.9moles  of Fe_2O_3

Thus CO is the limiting reagent as it limits the formation of product and Fe_2O_3 is the excess reagent.

As 3 moles of CO give = 2 moles of Fe  and 3 moles of CO_2

Thus 2.7 moles of CO will give =\frac{2}{3}\times 2.7=1.8moles  of Fe  and \frac{3}{3}\times 2.7=2.7moles  of CO_2

Thus 1.8 moles Fe and 2.7 moles CO_2 are produced.

7 0
3 years ago
Ethylenediamine (en) forms an octahedral complex with Ni2+(aq) with the formula [Ni(en)3]2+. Ni2+(aq) + 3 en ⇌ [Ni(en)3]2+(aq) K
yawa3891 [41]

Answer:

3.125\times 10^{-19} mol/L is the concentration of Ni^{2+}(aq) in the solution.

Explanation:

Ni^{2+}(aq) + 3 en\rightleftharpoons [Ni(en)_3]^{2+}(aq)

Concentration of nickel ion = [Ni^{2+}]=x

Concentration of nickel complex= [[Ni(en)_3]^{2+}]=\frac{0.16 mol}{2 L}=0.08 mol/L

Concentration of ethylenediamine = [en]=\frac{0.80 mol}{2 L}=0.40 mol/L

The formation constant of the complex = K_f=4.0\times 10^{18}

The expression of formation constant is given as:

K_f=\frac{[[Ni(en)_3]^{2+}]}{[Ni^{2+}][en]^3}

4.0\times 10^{18}=\frac{0.08 mol/L}{x\times (0.40 mol/L)^3}

x=\frac{0.08 mol/L}{4.0\times 10^{18}\times (0.40 mol/L)^3}

x=3.125\times 10^{-19} mol/L

3.125\times 10^{-19} mol/L is the concentration of Ni^{2+}(aq) in the solution.

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Answer:

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Explanation:

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