Question

what is the molar mass of calcium nitrate? write a correct formula of the compound before you answer the question.
204.18 g/mol
178.11 g/mol
164.1 g/mol
102.09 g/mol
question 5
10 pts
a substance has the molar mass of 225.19 g/mol. how many moles correspond to 0.700 g of that substance?
0.700 mol
158 mol
0.00311 mol
322 mol

Explanation:

Step1: Determine formula of calcium nitrate

Calcium has a +2 charge ($Ca^{2+}$) and nitrate has a -1 charge ($NO_3^{-}$), so the formula is $Ca(NO_3)_2$.

Step2: Calculate molar mass of $Ca(NO_3)_2$

The molar mass of Ca is 40.08 g/mol, N is 14.01 g/mol and O is 16.00 g/mol.
$M = 40.08+2\times(14.01 + 3\times16.00)$
$M=40.08 + 2\times(14.01+48.00)$
$M = 40.08+2\times62.01$
$M = 40.08 + 124.02$
$M=164.1$ g/mol

Step3: Calculate moles for second - part

The formula for moles $n=\frac{m}{M}$, where $m = 0.700$ g and $M = 225.19$ g/mol.
$n=\frac{0.700}{225.19}\approx0.00311$ mol

Answer:

For the first question: 164.1 g/mol
For the second question: 0.00311 mol