Calculating Moles in a CCl4 Sample: Step-by-Step Guide

Understanding how to calculate the number of moles in a given sample of a compound is a fundamental concept in chemistry. This guide will walk you through the process of finding the number of moles in a 100.0 gram sample of carbon tetrachloride (CCl4), a commonly used and studied chemical compound.

Understanding the Concept

The number of moles of a substance is a measure of how much of that substance is present in a given mass. This value is crucial in chemical equations and reactions. The formula to calculate the number of moles is:

moles frac{mass ; g}{molar ; mass ; g/mol}

Calculation of Molar Mass of CCl4

First, we need to calculate the molar mass of CCl4 (carbon tetrachloride). The molar mass is the sum of the atomic masses of all atoms in the molecule.

Carbon (C): 12.01 g/mol Chlorine (Cl): 35.45 g/mol

The formula for CCl4 is CCl4, so the molar mass is calculated as follows:

Molar ; mass ; of ; CCl4 (1 times 12.01) (4 times 35.45) 12.01 141.80 153.81 ; g/mol

Calculating the Number of Moles

Now, we can calculate the number of moles in a 100.0 gram sample of CCl4 using the formula:

moles frac{100.0 ; g}{153.81 ; g/mol} approx 0.651 ; moles

Therefore, there are approximately 0.651 moles in a 100.0 gram sample of CCl4.

General Steps to Solve Similar Problems

This kind of homework question can be solved in the following steps:

Calculate or look up the molecular mass of the compound (gram/mol). Using the given mass, calculate the number of moles: [moles frac{gram}{gram/mol}]. Checking units - Often, by examining the units of the numbers provided and the units of the quantities you need to calculate, you can find the required steps. For instance, to change from one unit to another (e.g., Ohm to Volt), you often need a value expressed in the ratio of the two (e.g., Volt/Ohm).

Additional Calculation for Further Understanding

The molecular weight of CCl4 is approximately 154 g/mol. Therefore, we can use this value to calculate the moles:

moles frac{100 ; g}{154 ; g/mol} 0.65 ; moles

This result is very close to our previous calculation, confirming the accuracy and consistency of the method.

Conclusion

Understanding how to calculate the number of moles in a substance is a key skill in chemistry. By following these steps and using the molar mass, you can solve similar problems efficiently. This guide covers both the calculation for a specific compound like CCl4 and provides a general approach to solving such problems.