Answer:
1120 L.
Explanation:
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In this case, as no conditions of pressure of temperature are given for this problem, we can assume that the scuba diver dives at STP (1 atm and 273.15 K), which means that 1 mole of air would occupy a volume of 22.4 L.
In such a way, since she needs 50.0 moles of air, the following ratio is useful to compute the size (volume) of the tank she needs:

Thereby, we plug in to obtain:

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Answer:
3.064 $
Solution:
First of all we will find the number of pounds contained by one Kg. Therefore, it is found that,
1 Kilogram = 2.20462 Pounds
Hence, as given,
1 Pound of Margarine costs = 1.39 Dollars
So,
2.20462 Pounds Margarine will cost = X Dollars
Solving for X,
X = (2.20462 Pounds × 1.39 Dollars) ÷ 1 Pound
X = 3.064 Dollars