<u>Answer:</u> The mass of iron (II) oxide that contains a million iron atoms is 
<u>Explanation:</u>
We are given:
Number of iron atoms = A million = 
The chemical formula of the given compound is 
It is formed by the combination of 2 iron atoms and 3 oxygen atoms.
According to mole concept:
1 mole of a compound contains
number of particles
1 mole of iron (II) oxide will contain =
number of iron atoms
We know that:
Molar mass of iron (II) oxide = 159.7 g/mol
Applying unitary method:
For
number of iron atoms, the mass of iron (II) oxide is 159.7 g
So, for
number of iron atoms, the mass of iron (II) oxide will be 
Hence, the mass of iron (II) oxide that contains a million iron atoms is 
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The volume of the sample of propane at STP is 0.62 mL.
<h3>What is volume?</h3>
Volume is the amount of space that a substance or object occupies.
To calculate the volume of gas at STP, we apply the formula below.
Formula:
- PV/T = P'V'/T'................. Equation 1
Where:
- P = Initial pressure of gas
- V = Initial volume of gas
- T = Initial temperature of gas
- P' = Standard pressure (SP)
- T' = Standard temperature (ST)
- V' = Volume of gas at STP.
Make V' The subject of the equation
- V' = PVT'/P'T.............. Equation 2
From the question,
Given:
- P = 320 torr
- V = 1.73 mL
- T = 30 °C = (30+273) K = 303 K
- P' = 760 torr
- T' = 273 K
Substitute these values into equation 2
- V' = (320×1.73×273)/(760×303)
- V' = 0.62 mL
Hence, the volume of the sample of propane at STP is 0.62 mL.
Learn more about volume here: brainly.com/question/26507715