Question

question 4 (1 point) saved
how many molecules of trinitrogen dichlorine occupy 804.2 l at stp?
2.16×10^24
3.60×10^25
2.16×10^25
1.93×10^25
question 5 (1 point) saved
if you have 453.2 g of a substance q, what is the gas density at stp if there are 6.751 mol of this substance?
6.75 g/l
4.34 g/l
3.20 g/l
2.99 g/l
question 6 (1 point) saved
the gas density of an unknown formula unit is 5.891 g/l at stp. how many atoms are in 51.56 grams of it?
2.35×10^23 atoms
4.70×10^23 atoms
5.89×10^22 atoms
1.17×10^24 atoms

Explanation:

Question 4

Step1: Recall molar - volume at STP

At STP, 1 mole of any gas occupies 22.4 L. Let $n$ be the number of moles of trinitrogen dichlorine. We know that $V = n\times V_m$, where $V = 804.2$ L and $V_m=22.4$ L/mol. So, $n=\frac{V}{V_m}=\frac{804.2}{22.4}$ mol.

Step2: Calculate the number of molecules

The number of molecules $N$ is given by $N = n\times N_A$, where $N_A = 6.022\times 10^{23}$ molecules/mol. First, $n=\frac{804.2}{22.4}\approx35.99$ mol. Then $N = 35.99\times6.022\times 10^{23}\approx2.16\times 10^{25}$ molecules.

Step1: Calculate the volume of the gas at STP

At STP, 1 mole of any gas occupies 22.4 L. If there are $n = 6.751$ mol of the substance, then the volume $V=n\times22.4$ L/mol. So, $V = 6.751\times22.4=151.2224$ L.

Step2: Calculate the density

Density $
ho=\frac{m}{V}$, where $m = 453.2$ g and $V = 151.2224$ L. So, $
ho=\frac{453.2}{151.2224}\approx2.99$ g/L.

Step1: Calculate the volume of the gas

We know that $
ho=\frac{m}{V}$, so $V=\frac{m}{
ho}$. Given $m = 51.56$ g and $
ho = 5.891$ g/L, then $V=\frac{51.56}{5.891}\approx8.753$ L.

Step2: Calculate the number of moles

At STP, $n=\frac{V}{22.4}$ L/mol. So, $n=\frac{8.753}{22.4}\approx0.391$ mol.

Step3: Calculate the number of atoms

Assume it is a monatomic gas (if not specified, we use this assumption for calculating the number of atoms). The number of atoms $N=n\times N_A$, where $N_A = 6.022\times 10^{23}$ atoms/mol. So, $N=0.391\times6.022\times 10^{23}\approx2.35\times 10^{23}$ atoms.

Answer:

C. $2.16\times 10^{25}$

Question 5