Question

3.) how many formula units (particles of agno₃) are in 5.50 grams of agno₃? (1 point)
8.67 x 10²¹ formula units
0.0032 formula units
6.14 and 10²² formula units
1.93 x 10²² formula units
4.) how many molecules are in 5.00 grams of nh₃? (1 point)
0.333
6.68 x 10²² molecules
1.77 x 10²³ molecules
2.00 x 10²¹ molecules
5.) how many molecules is 3.50 g co₂? (1 point)
4.79 x 10²² molecules co₂
1.44 x 10²³ molecules co₂
0.0795 molecules co₂
44 molecules co₂

Explanation:

Step1: Calculate molar mass of $AgNO_3$

The molar mass of $Ag$ is approximately $107.87\ g/mol$, $N$ is $14.01\ g/mol$ and $O$ is $16.00\ g/mol$. So molar mass of $AgNO_3=107.87 + 14.01+3\times16.00=169.88\ g/mol$.

Step2: Calculate moles of $AgNO_3$

Use the formula $n=\frac{m}{M}$, where $m = 5.50\ g$ and $M = 169.88\ g/mol$. So $n=\frac{5.50}{169.88}\approx0.0324\ mol$.

Step3: Calculate formula - units

Use Avogadro's number $N_A = 6.022\times 10^{23}\ formula - units/mol$. So the number of formula - units $N=n\times N_A=0.0324\times6.022\times 10^{23}\approx1.95\times 10^{22}$ formula - units. The closest answer is $1.93\times 10^{22}$ formula - units.

Step1: Calculate molar mass of $NH_3$

The molar mass of $N$ is $14.01\ g/mol$ and $H$ is $1.01\ g/mol$. So molar mass of $NH_3=14.01 + 3\times1.01=17.04\ g/mol$.

Step2: Calculate moles of $NH_3$

Use the formula $n=\frac{m}{M}$, where $m = 5.00\ g$ and $M = 17.04\ g/mol$. So $n=\frac{5.00}{17.04}\approx0.293\ mol$.

Step3: Calculate number of molecules

Use Avogadro's number $N_A = 6.022\times 10^{23}\ molecules/mol$. So the number of molecules $N=n\times N_A=0.293\times6.022\times 10^{23}\approx1.76\times 10^{23}$ molecules. The closest answer is $1.77\times 10^{23}$ molecules.

Step1: Calculate molar mass of $CO_2$

The molar mass of $C$ is $12.01\ g/mol$ and $O$ is $16.00\ g/mol$. So molar mass of $CO_2=12.01+2\times16.00 = 44.01\ g/mol$.

Step2: Calculate moles of $CO_2$

Use the formula $n=\frac{m}{M}$, where $m = 3.50\ g$ and $M = 44.01\ g/mol$. So $n=\frac{3.50}{44.01}\approx0.0795\ mol$.

Step3: Calculate number of molecules

Use Avogadro's number $N_A = 6.022\times 10^{23}\ molecules/mol$. So the number of molecules $N=n\times N_A=0.0795\times6.022\times 10^{23}\approx4.79\times 10^{22}$ molecules.

Answer:

D. $1.93\times 10^{22}$ formula units