Answer:
a) 1,6%
b) 64,775 g/mol
c) 3,6×10⁻² M
d) 2,3×10⁻³ g/mL
Explanation:
a) The mass fractium of helium is obtained converting the moles of the four gases to grams with molar weight and then caculating of the total of grams how many are of helium, thus:
- Helium: 0,25 moles ×
= 1 g of Helium - Argon: 0,25 moles ×
= 10 g of Argon - Krypton: 0,25 moles ×
= 20,95 g of krypton - Xenon: 0,25 moles ×
= 32,825 g of Xenon
Total grams: 1g+10g+20,85g+30,825g= 62,675 g
Mass fraction of helium: 
× 100 = <em>1,6%</em>
<em />
<em>The mass fraction of Helium is 1,6%</em>
<em />
<em>b)</em><em> </em>Because the mole fraction of all gases is the same the average molecular weight of the mixture is:
= 64,775 g/mol
c) The molar concentration is possible to know ussing ideal gas law, thus:
= M
Where:
P is pressure: 150 kPa
R is gas constant: 8,3145
T is temperature: 500 K
And M is molar concentration. Replacing:
M = 3,6×10⁻² M
d) The mass density is possible to know converting the moles of molarity to grams with average molecular weight and liters to mililiters, thus:
3,6×10⁻² 
× 
× 
=
2,3×10⁻³ g/mL
I hope it helps!
Burning and other changes in matter do not destroy matter. The mass of matter is always the same before and after the changes occur. The law of conservation of mass states that matter cannot be created or destroyed
Answer: B
Explanation: the answer is B
Answer: Physical change
Explanation: Condensation is the phase change of a gas to the liquid state. There is no formation of new products so it does not undergoes chemical change. Any phase change is considered a physical change.
<h3>Answer:</h3>
Option-D, "their elements have very similar properties and exhibit a clear trend" is the correct answer.
<h3>Explanation:</h3>
In periodic table the elements are arranged in tabular form with respect to their atomic masses, atomic numbers, electronic configurations and chemical properties. It is called periodic because the properties of elements repeats periodically.
Furthermore, the rows from left to right also called Periods basically shows the metallic and non metallic characters of elements. \those on the left are metals and those at the rights are non metals.
The columns from top to bottom are called as Groups. Groups contain elements of same chemical properties.
<h3>Example:</h3>
Group I elements are called as <em>Alkali Metals</em>. They all have one valence electron and hence, loose one electron to form the corresponding cation. i.e.
M → M⁺¹ + 1 e⁻
Group VII elements are called <em>Halogens</em>, they all are non metals and tend to gain one electron to form the corresponding halide ion. i.e.
X + 1 e⁻ → X⁻¹
