+1006 Hah, I'm just doing my chemistry homework right now on molar masses right now too, so I'll help. Fortunately (or unfortunately) for you, this means there will be a lot of details, and I don't use a lot lightly.
First, we have to find the molar mass of NaCl. We do this by finding the atomic mass of each element inside the compound: in this instance, Na (Sodium) and Cl (Chlorine). The atomic mass is the key shortcut here: the mole was made due to a number called Avogardo's number, which is the number of carbon-12 atoms in a gram of carbon-12. This number was found to be: $${\mathtt{6.022}}{\mathtt{\,\times\,}}{{\mathtt{10}}}^{{\mathtt{23}}}$$. This number is also generally accepted to be the number of any atom needed to make that given atom weigh a pound. Thus, one mole can be thought to be equivalent to the atomic mass of any given element.
Now that we've learned what Avogardo's number is and its relation to why we are using the atomic mass to determine the molar mass, we can continue onwards.
Sodium's atomic mass is about 22.99, and chlorine's atomic mass is about 35.45. This means each mole of sodium weighs about 22.99 grams, and that each mole of chlorine weighs about 35.45 grams. We now add these two numbers together.
$${\mathtt{22.99}}{\mathtt{\,\small\textbf+\,}}{\mathtt{35.45}} = {\frac{{\mathtt{1\,461}}}{{\mathtt{25}}}} = {\mathtt{58.44}}$$
And the total molar mass of sodium chloride (NaCl, table salt) is 58.44 grams/mole (conventionally shortened to 58.44 g/mol).
Now that we know the molar mass of NaCl, we can find how many grams are in 2.5 moles of NaCl.
A formula for moles → grams is as follows:
# of moles * molar mass/1 mole = # of grams
We know the number of moles (2.5) and now we have figured out the molar mass (58.44 g/mol). At this point, it is a matter of plugging it in.
$${\frac{{\mathtt{2.5}}{\mathtt{\,\times\,}}{\mathtt{58.44}}}{{\mathtt{1}}}} = {\frac{{\mathtt{1\,461}}}{{\mathtt{10}}}} = {\mathtt{146.1}}$$
The number of grams in 2.5 moles of NaCl is 146.1 grams
