# How many kilojoules of heat are needed to completely vaporize 42.8 g of C4H10O at its boiling point? Given Hvap=26.5kj/mol

## 15.3

## To calculate the amount of heat required to vaporize a given substance, we need to use the formula:

q = n * Hvap

Where:

q = amount of heat (in kilojoules)

n = number of moles of the substance

Hvap = molar heat of vaporization (in kilojoules per mole)

To find the number of moles (n), we can use the molar mass (M) of C4H10O (butanol).

First, let's calculate the molar mass of C4H10O:

C = 4 * 12.01 g/mol = 48.04 g/mol

H = 10 * 1.008 g/mol = 10.08 g/mol

O = 1 * 16.00 g/mol = 16.00 g/mol

Molar mass (M) of C4H10O = 48.04 + 10.08 + 16.00 = 74.12 g/mol

Now, let's find the number of moles (n) in 42.8 g of C4H10O:

n = mass / molar mass

n = 42.8 g / 74.12 g/mol

Now, we can calculate the amount of heat needed to vaporize C4H10O:

q = n * Hvap

q = (42.8 g / 74.12 g/mol) * 26.5 kJ/mol

Calculating the value of q:

q = (0.578 mol) * 26.5 kJ/mol

q = 15.307 kJ

Therefore, approximately 15.307 kilojoules (kJ) of heat are needed to completely vaporize 42.8 grams of C4H10O at its boiling point.

## To find the amount of heat needed to completely vaporize a substance, you can use the equation:

Q = m * Hvap

Where:

Q is the amount of heat (in kilojoules)

m is the mass of the substance (in grams)

Hvap is the molar heat of vaporization (in kilojoules per mole)

First, we need to convert the mass of C4H10O from grams to moles. To do this, we will use the molar mass of C4H10O.

The molar mass of C4H10O is calculated by adding the atomic masses of carbon (C), hydrogen (H), and oxygen (O) in the molecule:

C: 12.01 g/mol

H: 1.01 g/mol

O: 16.00 g/mol

Molar mass of C4H10O = (4 * 12.01) + (10 * 1.01) + (16.00) = 74.14 g/mol

Next, we can calculate the number of moles of C4H10O by dividing the mass by the molar mass:

Number of moles = mass / molar mass

Number of moles = 42.8 g / 74.14 g/mol

Now we can calculate the amount of heat using the equation Q = m * Hvap. Since Hvap is given in kilojoules per mole, we need to convert the moles of C4H10O to moles:

Q = (42.8 g / 74.14 g/mol) * 26.5 kj/mol

Now we can calculate the value of Q:

Q = (0.578 mol) * 26.5 kj/mol

Q = 15.307 kj

Therefore, the amount of heat needed to completely vaporize 42.8 g of C4H10O at its boiling point is approximately 15.307 kilojoules.

## q = mass x heat vaporization

Change 42.8g to mols. mols = grams/molar mass