Answer:
a.
.
b.

c.

Explanation:
Hello,
In this case, considering that the valve is opened, we can use the Boyle's law in order to compute the final pressure of argon by considering its initial pressure and volume and a final volume of 5.0 L:

And the final pressure of helium:

Which actually are the partial pressure of both of them, it means that the total pressure is:
Finally, the mole fraction of each gas is computed by considering the Dalton's law:


Best regards.
B. We are in the cenzoic era so what previously had happen to cause the life we live today was a huge mass extinction.... hope this helps!!
Answer: -
15.55 M
35.325 molal
Explanation: -
Let the volume of the solution be 1000 mL.
Density of nitric acid = 1.42 g/ mL
Total Mass of nitric acid Solution = Volume of nitric acid x Density of nitric acid
= 1000 mL x 1.42 g/ mL
= 1420 g.
Percentage of HNO₃ = 69%
Amount of HNO₃ = 
= 979.8 g
Molar mass of HNO₃ = 1 x 1 + 14 x 1 + 16 x 3 = 63 g /mol
Number of moles of HNO₃ = 
= 15.55 mol
Molarity is defined as number of moles per 1000 mL
We had taken 1000 mL as volume and found it to contain 15.55 moles.
Molarity of HNO₃ = 15.55 M
Mass of water = Total mass of nitric acid solution - mass of nitric acid
= 1420 - 979.8
= 440.2 g
So we see that 440.2 g of water contains 15.55 moles of HNO₃
Molality is defined as number of moles of HNO₃ present per 1000 g of water.
Molality of HNO₃ = 
= 35.325 molal
False. Eyeglasses do not cover all around the eye however safety goggles do
Holding items in the freezer for too long is not an example of abuse of time and temperature.
<h3>
What is abuse of time and temperature?</h3>
Abuse of time and temperature has to do with a situation in which time is used in an improper way or food is not held at the correct temperature ultimately leading to food poisoning.
Holding items in the freezer for too long is not an example of abuse of time and temperature.
Learn more about temperature: brainly.com/question/7510619