How many joules of heat are needed to completely vaporize 24.40g of H2O at its boiling point. Delta H vap = 40.6kJ/mol

To calculate the amount of heat needed to vaporize a given mass of a substance, you need to use the formula:

q = m × ΔHvap

Where:
- q is the amount of heat (in joules) required
- m is the mass of the substance (in grams)
- ΔHvap is the enthalpy of vaporization (in joules per gram)

First, you need to convert the given mass of water (H2O) to moles. This can be done using the molar mass of water, which is approximately 18.015 g/mol.

molar mass of H2O = 2(1.008 g/mol) + 16.00 g/mol = 18.015 g/mol

To convert grams to moles, divide the given mass by the molar mass:

moles of H2O = 24.40 g / 18.015 g/mol

Now you have the number of moles of water.

Next, you need to calculate the heat (q) using the formula mentioned above:

q = moles of H2O × ΔHvap

However, since the given value of ΔHvap is in kilojoules per mole (kJ/mol), it needs to be converted to joules per gram (J/g) for the calculations. To do this, divide the given ΔHvap value by the molar mass of water:

ΔHvap = 40.6 kJ/mol × 1000 J/kJ / 18.015 g/mol

Now you have the value of ΔHvap in joules per gram.

Finally, substitute the values into the formula to find the heat (q):

q = moles of H2O × ΔHvap

Calculating this will give you the amount of heat (in joules) needed to completely vaporize the given mass of water.

To determine the amount of heat required to completely vaporize a given amount of a substance, we can use the equation:

q = m * ΔHvap

where:
q is the amount of heat (in joules)
m is the mass of the substance (in grams)
ΔHvap is the molar heat of vaporization (in joules per mole)

First, we need to convert the mass of water to moles. The molar mass of water (H2O) is approximately 18.015 g/mol:

moles of H2O = mass of H2O / molar mass of H2O
moles of H2O = 24.40 g / 18.015 g/mol
moles of H2O ≈ 1.355 mol

Next, we can calculate the amount of heat required:

q = m * ΔHvap
q = 1.355 mol * 40.6 kJ/mol * (1000 J/1 kJ)
q ≈ 55,123 J

Therefore, approximately 55,123 joules of heat are needed to completely vaporize 24.40 grams of H2O at its boiling point.

hos many mols do you have? That's mols = grams/molar mass = ?

Convert kJ/mol to J/mol
Then mols H2O x heat vap(in J/m) = q