Use a ratio to find out that x/190.2 = 74.5/100
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Answer:

Explanation:
Hello,
In this case, we can consider that the given heat of combustion is indeed the heat of reaction since it corresponds to the combustion of propane, which is computed by using the heat formation of all the involved species as shown below:

Thus, since the heat of formation of gaseous carbon dioxide is -393.5 kJ/mol, water -241.8 kJ/mol and oxygen 0 kJ/mol, the heat of formation of propane is:

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Answer:
mass ( g ) = 348 g
Explanation:
First you know : M = mole / volume (L)
in question you have the M and V and the formula of SUBSTANCE ( KF )
first you get the number of mole from equation above
so 3 = no of mole / 2
no of mole = 3 × 2 = 6 moles
and the moles equation is no of moles = mass ( g ) / molecular weight ( g/mole )
so you have already calculate the moles and you can know the MW from the Question
Mw of KF = 39 + 19 = 58
so n = mass / MW
so 6 = mass / 58
mass ( g ) = 348 g
GOOD LUCK
14 - 2nd one
15 - I do not know
16 - also do not know
Sorry