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viktelen [127]
2 years ago
12

What is the number of moles in 15.0 g AsH3?

Chemistry
1 answer:
Grace [21]2 years ago
7 0

Answer:

0.192 mol.

Explanation:

  • To calculate the no. of moles of a substance (n), we use the relation:

<em>n = mass / molar mass.</em>

mass of AsH₃ = 15.0 g.

molar mass of AsH₃ = 77.95 g/mol.

∴ The number of moles in 15.0 g AsH₃ = mass / molar mass = (15.0 g) / (77.95 g/mol) = 0.192 mol.

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Drinking water may contain a low concentration of lead ion (Pb2 ) due to corrosion of old lead pipes. The EPA has determined tha
Lynna [10]

Answer:

3.861x10⁻⁹ mol Pb⁺²

Explanation:

We can <u>define ppm as mg of Pb²⁺ per liter of water</u>.

We<u> calculate the mass of lead ion in 100 mL of water</u>:

  • 100.0 mL ⇒ 100.0 / 1000 = 0.100 L
  • 0.100 L * 0.0080 ppm = 8x10⁻⁴ mg Pb⁺²

Now we <u>convert mass of lead to moles</u>, using its molar mass:

  • 8x10⁻⁴ mg ⇒ 8x10⁻⁴ / 1000 = 8x10⁻⁷ g
  • 8x10⁻⁷ g Pb²⁺ ÷ 207.2 g/mol = 3.861x10⁻⁹ mol Pb⁺²
4 0
2 years ago
The concentration of Si in an Fe-Si alloy is 0.25 wt%. What is the concentration in kilograms of Si per cubic meter of alloy?
kodGreya [7K]

Answer : The concentration of Si in kilograms is, 19.55kg/m^3

Explanation :

As we are given that, the concentration of Si in an Fe-Si alloy is 0.25 wt% that means:

Weight of Si = 0.25 g = 0.00025 kg

Weight of Fe = 100 - 0.25 = 99.75 g = 0.09975 kg

Density of Si = 2.32g/cm^3=2.32\times 10^6g/m^3

Density of Fe = 7.87g/cm^3=7.87\times 10^6g/m^3

Now we have to calculate the concentration in kilograms of Si per cubic meter of alloy.

Concentration of Si in kilograms =  \frac{\text{Weight of Si in 100 g of alloy}}{\text{Volume of 100 g of alloy}}

Concentration of Si in kilograms =  \frac{\text{Weight of Si in 100 g of alloy}}{\frac{\text{Wight of Fe}}{\text{Density of Fe}}+\frac{\text{Wight of Si}}{\text{Density of Si}}}

Now put all the given values in this expression, we get:

Concentration of Si in kilograms = \frac{0.00025kg}{\frac{99.75g}{7.87\times 10^6g/m^3}+\frac{0.25g}{2.23\times 10^6g/m^3}}

Concentration of Si in kilograms = 19.55kg/m^3

Thus, the concentration of Si in kilograms is, 19.55kg/m^3

5 0
2 years ago
A planet travels in an elliptical path around a star, as shown in the figure. As the planet gets closer to the star, the gravita
Soloha48 [4]

Answer:

The force increases because it is part of a Newton’s third law pair of forces with the force that the star exerts on the planet.

Explanation:

Force between two objects can be expressed by an equation:

F = G • m1 • m2 / r^2,

where m1 and m2 are objects' masses, r is the distance between them, and G is a gravitational constant.

That means that greater the masses or lesser the distance, the force will be greater, and vice versa.

This force exists between any two objects, but is generally extremely weak, so it's best observed with big and large objects with great mass, such as planets and stars.

This force, whatever its magnitude may be, always works on both objects, following the third Newton's law.

So, whatever the force the stat exerts on the planet is, the planet will exert the same amount of force on the star.

3 0
2 years ago
84. Heavy water, D2O (molar mass = 20.03 g mol–1), can be separated from ordinary water, H2O (molar mass = 18.01), as a result o
ipn [44]

Answer:

relative rate of diffusion is 1.05

Explanation:

According to Graham's law of difussion:

Rate of diffusion is inversely proportional to the square root of molecular weight of a molecule.

For two given molecules:

\frac{(rate)_{1}}{(rate)_{2}}=\frac{\sqrt{M_{2}} }{\sqrt{M_{1}}}

The given molecules are

Water = 18.01

Heavy water =20.03

Thus the relative rate of diffusion will be:

\frac{(rate)_{water}}{(rate)_{heavywater}}=\sqrt{ \frac{20.03}{18.01}}=1.05

8 0
2 years ago
Which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molec
ValentinkaMS [17]

Answer:

d.) Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause electrons in the molecules to increase their electronic energy states.

Explanation:

Microwave: transitions in the molecular rotational levels

Infrared: transitions in molecular vibrational levels

UV/Visible: transitions in electronic energy levels.

5 0
1 year ago
Read 2 more answers
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