Question

directions: solve each of the following problems 7 - 12 as directed. show all your work (using dimensional analysis on #s 9 - 12) then bold and underline your final answer. 7.) find the molar mass of bacl₂. (3 points) 8.) find the molar mass of ca₃(po₄)₂. (3 points) 9.) how many molecules of caco₃ are present in 10.8 mol of calcium carbonate, (caco₃)? (3 points)

Explanation:

7.

Step1: Identify atomic masses

The atomic mass of Ba is approximately 137.33 g/mol and Cl is approximately 35.45 g/mol.

Step2: Calculate molar mass of $BaCl_2$

The molar mass $M$ of $BaCl_2$ is $M = 1\times137.33+ 2\times35.45$.
$M=137.33 + 70.9=208.23$ g/mol

Step1: Identify atomic masses

The atomic mass of Ca is approximately 40.08 g/mol, P is approximately 30.97 g/mol, and O is approximately 16.00 g/mol.

Step2: Calculate molar mass of $Ca_3(PO_4)_2$

For $Ca_3(PO_4)_2$, we have 3 Ca atoms, 2 P atoms and 8 O atoms.
$M = 3\times40.08+2\times30.97 + 8\times16.00$
$M=120.24+61.94 + 128.00$
$M = 310.18$ g/mol

Step1: Use Avogadro's number

Avogadro's number $N_A=6.022\times 10^{23}$ molecules/mol.

Step2: Calculate number of molecules

The number of molecules $N$ of $CaCO_3$ is given by $N = n\times N_A$, where $n = 10.8$ mol.
$N=10.8\times6.022\times 10^{23}$
$N = 6.50376\times 10^{24}$ molecules

Answer:

$\mathbf{208.23\ g/mol}$

8.