First calculate for the molar mass of the given formula unit, CaCO₃. This can be done by adding up the product when the number of atom is multiplied to its individual molar mass as shown below.

molar mass of CaCO₃ = (1 mol Ca)(40 g Ca/mol Ca) + (1 mol C)(12 g of C/1 mol of C) + (3 mols of O)(16 g O/1 mol O) = 100 g/mol of CaCO₃

Then, divide the given amount of substance by the calculated molar mass.
number of moles = (20 g)(1 mol of CaCO₃/100 g)
number of moles = 0.2 moles of CaCO₃

Answer: 0.2 moles

6 0

3 years ago

Why was the line of best fit method used to determine the experimental value of absolute zero?

BartSMP [9]

Answer:

Because the x-intercet of the graph represents volume zero, which indicates the minimum possible temperature or absolute zero.

Explanation:

Charle's Law for ideal gases states that, at constant pressure, the temperature and the volume of a sample of gas are protortional.

$\dfrac{V}{T}=k\\\\V=kT$

That means that the graph of the relationship between Temperature, in Kelivn, and Volume is a line, which passes through the origin.

When you work with Temperature in Celsius, and the temperature is placed on the x-axis, the line is shifted to the left 273.15ºC.

Meaning that the Volume at 273.15ºC is zero.

You cannot reach such low temperatures in an experiment, and also, volume zero is not real.

Nevertheless, you can draw the line of best fit and extend it until the x-axis (corresponding to a theoretical volume equal to zero), and read the corresponding temperature.

Subject to the experimental errors, and the fact that the real gases are not ideal, the temperature that you read on the x-axis is the minimum possible temperature (absolute zero) as the minimum possible volume is zero.

3 0

3 years ago