Calculating molar mass and moles is an important part of chemistry, but many students find it difficult. It’s easy to make mistakes that can lead to big errors in your final answers.

One common mistake is not paying attention to significant figures. This means you should be careful about how many numbers you keep after the decimal point. For example, if you add the weights of carbon (12.01 g/mol) and oxygen (16.00 g/mol), make sure your final answer has the right number of decimal places.

Another mistake is getting moles and molar mass mixed up. Molar mass (measured in g/mol) tells you how much one mole of a substance weighs. On the other hand, moles (represented by the letter $n$) show how many of those particles you have. The formula to connect these two is pretty simple:

$n = \frac{mass (g)}{molar \ mass (g/mol)}$

Some students mix up this formula by accidentally switching the top and bottom numbers, which can lead to incorrect results.

Also, forgetting about diatomic elements can be confusing. For example, oxygen is often written as O, but it actually exists as O$_2$ in nature. This means you have to double the molar mass for calculations. So, O (16.00 g/mol) becomes O$_2$ (32.00 g/mol). If you forget this step, you can make a big mistake in your calculations.

Lastly, students sometimes rush through their calculations. This can lead to silly math mistakes. Whether you’re adding numbers or using a conversion factor, taking a moment to check your work can save you time and trouble later.

By avoiding these mistakes, you'll find it easier to master molar mass and moles!