The molar heat of fusion of platinum (pt) is 4.700 kcal/mol. how much heat must be added to 85.5 g of
solid platinum at its melting point to completely melt it?
w kcal

2.07 Kcal heat must be added to completely melt the platinum.

Explanation:

Given data:

Molar heat of fusion =  4.700 Kcal / mol

Mass of platinum = 85.5 g

Heat of fusion = ?

Solution:

Formula:

ΔH = n × molar heat of fusion

n = number of moles

Now we will calculate the number of moles:

Number of moles = mass / molar mass

Number of moles = 85.5 g /195.08 g/mol

Number of moles = 0.44 mole

ΔH = n × molar heat of fusion

ΔH = 0.44 mol × 4.700 Kcal / mol

ΔH = 2.07 Kcal

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2

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