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kumpel [21]
3 years ago
12

A materials scientist has created an alloy containing aluminum, copper, and zinc, and wants to determine the percent composition

of the alloy. The scientist takes a 13.039 g sample of the alloy and reacts it with concentrated HCl . The reaction converts all of the aluminum and zinc in the alloy to aluminum chloride and zinc chloride in addition to producing hydrogen gas. The copper does not react with the HCl . Upon completion of the reaction, a total of 11 L of hydrogen gas was collected at a pressure of 744 torr and a temperature of 27.0 °C . Additionally, 2.761 g of unreacted copper is recovered. Calculate the mass of hydrogen gas formed from the reaction.
Chemistry
1 answer:
liubo4ka [24]3 years ago
7 0

Answer:

0.8749 grams of hydrogen gas was formed from the reaction.

Explanation:

P = Pressure of hydrogen gad= 744 Torr = 0.98 atm

(1 atm = 760 Torr)

V = Volume of hydrogen gas= 11 L

n = number of moles of hydrogen gas= ?

R = Gas constant = 0.0821 L.atm/mol.K

T = Temperature of vapor = 27.0 °C = 300.15 K

Putting values in above equation, we get:

Using an ideal gas equation:

PV=nRT

n=\frac{PV}{RT}=\frac{0.98 atm\times 11 L}{0.0821 L atm/mol K\times 300.15 K}

n = 0.4374 moles

Mass of 0.4374 moles of hydrogen gas:

0.4374 mol × 2 g/mol = 0.8749 g

0.8749 grams of hydrogen gas was formed from the reaction.

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We are given with
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Using stoichiometry
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3 years ago
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Carbonyl fluoride, COF2, is an important intermediate used in the production of fluorine-containing compounds. For instance, it
kvasek [131]

Answer:

0.396 M

Explanation:

Let's consider the following reaction.

2 COF₂(g) ⇌ CO₂(g) + CF₄(g)

We can find the concentrations at equilibrium using an ICE Chart.

         2 COF₂(g) ⇌ CO₂(g) + CF₄(g)

I            2.00              0            0

C           -2x                +x          +x

E         2.00-2x            x             x

The concentration equilibrium constant (Kc) is:

Kc=4.10=\frac{[CO_{2}][CF_{4}]}{[COF_{2}]^{2} } =\frac{x^{2} }{(2.00-2x)^{2} } =(\frac{x}{2.00-2x} )^{2} \\\sqrt{4.10} = \frac{x}{2.00-2x}\\4.05-4.05x=x\\x=0.802

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4 0
3 years ago
Josh is doing an experiment with water. He starts with a plastic cup of water that has a mass of 12 grams. He places the cup in
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Answer: A) The mass of the cup of frozen water is 12 grams which means the mass did not change


Explanation:


The mass of water did not change, because the amount of matter is the same: by the law of mass conservation you can assure that the mass of water (12 grams) is the same at the begining than the end.


Both in the physical changes (as in the case of the changes in the phases of the matter) and in the chemical changes, the law of conservation of the mass is obeyed. Therefore, assuming that the liquid water did not spill from the sealed container during the night, the mass remained constant (12 grams).


Regarding the fact that Josh noticed the cup had cracked on its sides, you must observe that water is an exception to the common behavior of the matter: most substances shrink when pass from liquid state to solid state due to the fact that the particles (atoms, molecules or ions) lose kinetic energy and they the approach each other occupying less space.


Being the density inversely relatated to the volume (density = mass / volume), this increase on volume means that the substances will increase its density when pass from liquid to solid.


But water is a remarkable exception. Water density reaches its maximum at about 4°C, which means that solid water (0°C) is less dense than liquid water.


Hence, ice (solid water) will ocuppy more space (more volume) than the same amount of liquid water, which is the reason why the liquid water in the plastic cup expanded when it froze, cracking the cup.


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3 years ago
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