The density of water is 1.00 g/ml at 4°c. how many water molecules are present in 2.56 ml of water at this temperature?

8.55 * 10²² Molecules

Solution:

Step 1: Calculate the Mass of Water as;

Density = Mass : Volume

Solving for Mass,

Mass = Density * Volume

Putting values,

Mass = 1 g. mL⁻¹ * 2.56 mL

Mass = 2.56 g

Step 2: Calculate Moles of Water as,

Moles = Mass : M. Mass

Putting values,

Moles = 2.56 g : 18 g. mol⁻¹

Moles = 0.142 mol

Step 3: Calculate Number of Molecules of Water as,

# of Molecules = Moles * 6.022 * 10²³

Putting value of mole,

# of Molecules = 0.142 * 6.022 * 10²³

# of Molecules = 8.55 * 10²² Molecules