Answer:
Explanation:
Li(s)+1/2 F₂(g)→LiF(s)
In this reaction one mole of product is formed from gaseous state of reactants . So this reaction will represent the reaction for which ΔH∘rxn equals to ΔH∘f .
In other reaction one mole is not produced if we balance the reaction. The reactant must be in gaseous state . ΔH∘f . represents heat of formation . ΔH∘rxn represents heat of reaction .
The mass of pentane the student should weigh out is
The density of pentane is 0.626 gcm-3
To calculate the mass of pentane following expression is used,
(Density is defined as the mass divide by volume)
Density = mass / volume
mass of pentane = Density of pentane * Volume of pentane
mass of pentane = 0.626 gcm-3 * 45.0 mL
= 28.17 g
Here the unit of mass of pentane is g,
However the unit of density is gcm-3 and unit of volume is mL i.e. cm3
Hence, Mass = gcm-3 * cm3
Mass = g
The mass of pentane the student should weigh out is 28.17g
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