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REY [17]
2 years ago
7

Which change of phase is endothermic chem test.

Chemistry
1 answer:
nikdorinn [45]2 years ago
5 0

Answer:

Melting is an example of an endothermic change.

Explanation:

This is because the system absorbs (heat) energy from the surroundings to increase its temperature.

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A glass container was initially charged with
vichka [17]

The number of moles of the gas sample present at the end is 0.78 moles.

<h3>Number of moles of the gas</h3>

PV = nRT

V = nRT/P

At a constant volume, V;

n₁RT₁/P₁ = n₂RT₂/P₂

n₁T₁/P₁ = n₂T₂/P₂

n₂ = (n₁T₁P₂)/(P₁T₂)

where;

  • T₁ is initial temperature = 21.7⁰C = 294.7 K
  • T₂ is final temperature = 28.1⁰C = 301.1 K

n₂ = (3 x 294.7 x 0.998)/(3.75 x 301.1)

n₂ = 0.78 moles

Thus, the number of moles of the gas sample present at the end is 0.78 moles.

Learn more about number of moles here: brainly.com/question/15356425

#SPJ1

8 0
3 years ago
For many purposes we can treat methane as an ideal gas at temperatures above its boiling point of . Suppose the temperature of a
Elza [17]

Answer:

The volume decreases 5.5%

Explanation:

First, the question is incomplete, you are not giving the values of the temperatures and the pressure. However, I managed to find one similar question, and the given data is the temperature is lowered from 21 °C to -8°C, and the pressure decreased by 5%. If your data is different, you should only replace your data in the procedure, and you'll get an accurate result.

Now, with this data, let's see what we can do.

If this is an ideal gas, the equation to use is:

PV = nRT

Now, we know that this gas is suffering a decrease in temperature and pressure, but the moles stay the same so:

n₁ = n₂ = n

The constant R, is the same for both conditions. The only thing that differs here is the volume, temperature, and pressure. Therefore:

P₁V₁ = nRT₁   -----> n = P₁V₁ / RT₁

Doing the same with the pressure and volume 2 we have:

n = P₂V₂ / RT₂

Equalling both expressions and solving for V₂:

P₁V₁ / RT₁ = P₂V₂ / RT₂

V₂ = P₁T₂V₁ / P₂T₁

Now, as we know that P2 is 5% decreased from P1, so P2 = 0.95P1:

V₂ = P₁T₂V₁ / 0.95P₁T₁

The values of temperature in K:

T1 = 21+273 = 294 K

T2 = -8 + 273 = 265 K

Finally, let's calculate the volume:

V₂ = 264*P₁*V₁ / 294*0.95*P₁   ----> P cancels out  

V₂ = 264V₁ / 294*0.95

V₁ = 0.945V₂

With this, we can day that Volume 2 decreases.

Now the percentage change would be using the following expression:

%V = (V₁ - V₂ / V₁) * 100

Replacing the data we have:

%V = V1 - 0.945V₁ / V₁

%V = 0.055V₁ / V₁ * 100

%V = 5.5%

7 0
3 years ago
A substance with a higher specific heat will take more energy to raise its temperature ?
Wewaii [24]
This is true, well done.
7 0
3 years ago
Suppose water contained some harmful volatile substance. How could you easily remove the volatile substance in a laboratory?
kari74 [83]
Well, you could use a reverse osmosis process to remove all of the fluoride that the United Staes government has put in the water! Every year the Us Gov receives a lot of fluoride from china. Fluoride is a waste and a poison, and instead of the Us Government paying a Buch of money to burn this waste, they just put it in the water! what you need t do, is get your water from the earth. Which is actually the best place to get your water, because its WATER filtered by the earth. Just google wells or springs around your location, some private business/companies offer their water collecting serves, something you should really take advantage of! As for me, I get my water at a place called "Carlsbad alkaline water." good stuff, only 50 cents for 4 gallons. rawr XD  Jesus loves you, and he offers the everything freely, which means you don't need to follow a religion to earn anything. Lets face it, your not perfect, and we need help from God! 
6 0
4 years ago
What about these questions
Oksanka [162]
Again great job! They all look correct except 20. is 3.7 due to sig fig of least precision, which you have a mark by!! You don't even need help!;) Here comes the next chemical engineer! :)
4 0
4 years ago
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