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Zielflug [23.3K]
3 years ago
5

A gallon of water has a mass of 3.79 kg. how many moles of water (18.02 g/mol) is this?

Chemistry
2 answers:
Stels [109]3 years ago
6 0
<span>210. moles To determine the number of moles of a substance you have, simply divide the mass of the substance you have by its molar mass. So 3.79 kg / 18.02 g/mol = 3790 g / 18.02 g/mol = 210.3218646 mol Since we only have 3 significant figures, the answer should be rounded to 3 figures, giving 210. as the result. Notice that the decimal point is required. If you state the number of moles is 210, then that answer will only have 2 significant figures. But the value of 210. has 3 significant figures.</span>
garik1379 [7]3 years ago
3 0
First, we will convert the mass of the gallon to grams:
a gallon of water has a mass of 3.79 * 1000 = 3790 grams of water

number of moles can be calculated using the following rule:
number of moles = mass / molar mass
Therefore,
number of moles = 3790 / 18.02 = 210.32 moles
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Answer:

0.35 V

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                            <u> E°/V</u>

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Cr³⁺ + 3e⁻ ⇌ Cr; -0.74

(b) Standard cell potential

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2Cr³⁺ + 6e⁻ ⇌ 2Cr;               +0.74

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3. Cell potential

2Cr³⁺(0.75 mol·L⁻¹) + 6e⁻ ⇌ 2Cr

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2Cr³⁺(0.75 mol·L⁻¹) + 3Fe ⇌ 2Cr + 3Fe²⁺(0.25 mol·L⁻¹)

The concentrations are not 1 mol·L⁻¹, so we must use the Nernst equation

E = E^{\circ} - \dfrac{RT}{zF}\ln Q

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  E° = 0.33 V

   R = 8.314 J·K⁻¹mol⁻¹

   T = 298 K

   z = 6

   F = 96 485 C/mol

(b) Calculations:  

Q = \dfrac{\text{[Fe}^{2+}]^{3}}{ \text{[Cr}^{3+}]^{2}} = \dfrac{0.25^{3}}{ 0.75^{2}} =\dfrac{0.0156}{0.562} = 0.0278\\\\E = 0.33 - \left (\dfrac{8.314 \times 298}{6 \times 96485}\right ) \ln(0.0278)\\\\=0.33 -0.00428 \times (-3.58) = 0.33 + 0.0153 = \textbf{0.35 V}\\\text{The cell potential is }\large\boxed{\textbf{0.35 V}}

 

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The pressure of a gas depends on the temperature and volume of the gas.

<h3>Ideal gas equation</h3>

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