How do you determine the formula and molar mass of silver cyanide?

1 Answer
Dec 26, 2016

Answer:

Identify the bond and participating atoms.

Add the atomic mass of all elements present.

Explanation:

Formula

You must identify the type of bond(s) present. In this case, it is an ionic compound.

You must also identify the elements/polyatomic ions present. In this case, there is silver (#Ag#), and cyanide (#CN#).
- If there was a multivalent element, you have to look at the chemical name. If there are Roman numerals, then the preceding element is multivalent with a charge of whatever the numerals indicate. E.g. #CuSO_"4"# = Copper (II) sulfate -> the subscripts were reduced.

Knowing that it is an ionic compound, we know that the electrons are transferred. Thus the cation goes first (#Ag#), then the anion (#CN#). The charges are #1+# and #1-#, therefore we do not need to reduce.

We get #AgCN#.


Molar mass

You need a periodic table for this. The molar mass of a compound is simply the sum of all elements in the compound (including the subscripts if any; no coefficients if any).

#Ag# has a atomic mass of #107.87 mu#
#C# has a atomic mass of #12.01 mu#
#N# has a atomic mass of #14.01 mu#

Add them all up and you get #133.89 g/(mol)#. There is a reason why the units for atomic mass and molar mass are different. Once you learn about mols and such, you will know why, so I will leave that to your teacher.

Hope this helps :)