The density of liquid mercury is 13.6 g/cm³. How many moles of mercury are there in 1 litre of the metal? (atomic mass of Hg = 200 g/mol)

(A) 55

(B) 13.6

(C) 68

(D) none of these.

To determine how many moles of mercury are present in 1 liter of the liquid metal, we can follow a straightforward calculation using the density and the atomic mass of mercury. Let's break it down step by step.

Understanding Density and Volume

The density of a substance is defined as its mass per unit volume. In this case, the density of liquid mercury is given as 13.6 g/cm³. Since we are working with 1 liter of mercury, we need to convert liters to cubic centimeters because the density is provided in grams per cubic centimeter.

Conversion of Volume

1 liter is equivalent to 1000 cubic centimeters (cm³). Therefore, we can say:

• Volume of mercury = 1 L = 1000 cm³

Calculating Mass

Now that we have the volume, we can calculate the mass of mercury using the formula:

Mass = Density × Volume

Substituting the known values:

Mass = 13.6 g/cm³ × 1000 cm³

This gives us:

Mass = 13600 g

Finding Moles of Mercury

Next, we need to convert the mass of mercury into moles. The number of moles can be calculated using the formula:

Moles = Mass / Molar Mass

Given that the atomic mass of mercury (Hg) is 200 g/mol, we can substitute the values:

Moles = 13600 g / 200 g/mol

Calculating this gives:

Moles = 68

Final Answer

Thus, the number of moles of mercury in 1 liter of the metal is 68. Therefore, the correct choice from the options provided is (C) 68.