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RoseWind [281]
2 years ago
13

A 0.271 g sample of an unknown vapor occupies 294 ml at 140.°c and 847 mmhg. the empirical formula of the compound is ch2. what

is the molecular formula of the compound?
Chemistry
1 answer:
sdas [7]2 years ago
6 0
When the molar mass M = mass (g)/ no.of moles (Mol)

∴ moles= 0.271 g / M

By using the gas equation:

PV = n RT

when P is the pressure = 847 mmHg / 760 = 1.11 atm

V is the volume = 0.294 L

n = 0.271 / M

R is constant = 0.0821 

T= 140+273 = 413 K

so by substitution:

when n = PV/RT

∴ 0.271/ M = 1.11 atm *0.294 L/ 0.0821 *413

∴ M = 28 


when the empirical formula of CH2 = 12+2 = 14 

∴ the exact no.of moles = 28/14 = 2

∴the molecular formula = 2(CH2) = C2H4

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The half life of a certain radioactive element is 1,250 years what percent of the atoms remain after 7500 years
andrezito [222]
Each half-life results in ~50% (1/2) of the original element remaining.

7500/1250 = 6 half-lives, so 100(1/2)^6
= 100(0.015625)
= 1.5625% of the original element would remain
7 0
2 years ago
Read 2 more answers
one method for generating chlorine gas is by reacting potassium permanganate and hydrochloric acid. how many liters of Cl2 at 40
Ronch [10]

<u>Answer:</u> The volume of chlorine gas produced in the reaction is 2.06 L.

<u>Explanation:</u>

  • <u>For potassium permanganate:</u>

To calculate the number of moles, we use the equation:

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

Given mass of potassium permanganate = 6.23 g

Molar mass of potassium permanganate = 158.034 g/mol

Putting values in above equation, we get:

\text{Moles of potassium permanganate}=\frac{6.23g}{158.034g/mol}=0.039mol

  • <u>For hydrochloric acid:</u>

To calculate the moles of hydrochloric acid, we use the equation:

\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}

Molarity of HCl = 6.00 M

Volume of HCl = 45.0 mL = 0.045 L   (Conversion factor: 1 L = 1000 mL)

Putting values in above equation, we get:

6.00mol/L=\frac{\text{Moles of HCl}}{0.045L}\\\\\text{Moles of HCl}=0.27mol

  • For the reaction of potassium permanganate and hydrochloric acid, the equation follows:

2KMnO_4+16HCl\rightarrow 2MnCl_2+5Cl_2+2KCl+8H_2O

By Stoichiometry of the reaction:

16 moles of hydrochloric acid reacts with 2 moles of potassium permanganate.

So, 0.27 moles of hydrochloric acid will react with = \frac{2}{16}\times 0.27=0.033moles of potassium permanganate.

As, given amount of potassium permanganate is more than the required amount. So, it is considered as an excess reagent.

Thus, hydrochloric acid is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

16 moles of hydrochloric acid reacts with 5 moles of chlorine gas.

So, 0.27 moles of hydrochloric acid will react with = \frac{5}{16}\times 0.27=0.0843moles of chlorine gas.

  • To calculate the volume of gas, we use the equation given by ideal gas equation:

PV=nRT

where,

P = pressure of the gas = 1.05 atm

V = Volume of gas = ? L

n = Number of moles = 0.0843 mol

R = Gas constant = 0.0820\text{ L atm }mol^{-1}K^{-1}

T = temperature of the gas = 40^oC=[40+273]K=313K

Putting values in above equation, we get:

1.05atm\times V=0.0843\times 0.0820\text{ L atm }mol^{-1}K^{-1}\times 313K\\\\V=2.06L

Hence, the volume of chlorine gas produced in the reaction is 2.06 L.

3 0
2 years ago
Which of the following atoms would have the longest de Broglie wavelength, if all have the same velocity?
GenaCL600 [577]

Answer:

Li

Explanation:

The phenomenon of wave particle duality was well established by Louis deBroglie. The wavelength associated with matter waves was related to its mass and velocity as shown below;

λ= h/mv

Where;

λ= wavelength of matter waves

m= mass of the particle

v= velocity of the particle

This implies that if the velocities of all particles are the same, the wavelength of matter waves will now depend on the mass of the particle. Hence; the wavelength of a matter wave associated with a particle is inversely proportional to the magnitude of the particle's linear momentum. The longest wavelength will then be obtained from the smallest mass of matter. Hence lithium which has the smallest mass will exhibit the longest DeBroglie wavelength

4 0
2 years ago
Calculate the heat change in calories for melting 65 g of ice at 0 ∘c.
Genrish500 [490]

When ice melts, the physicals state changes from solid to liquid. The energy or the heat required (q) required to change a unit mass (m) of a substance from solid to liquid is known as the enthalpy or heat of fusion (ΔHf). The variables; q, m and ΔHf are related as:

q = m * ΔHf

the mass of ice m = 65 g

the heat of fusion of water at 0C = ΔHf = 334 J/g

Therefore: q = 65 g * 334 J/g = 21710 J

Now:

4.184 J = 1 cal

which implies that: 21710 J = 1 cal * 21710 J/4.184 J = 5188.8 cal

Hence the heat required is 5188.8 cal or 5.2 Kcal (approx)

5 0
2 years ago
The Safe Drinking Water Act (SDWA) sets a limit for mercury-a toxin to the central nervous system-at 0.002 mg/L. Water suppliers
posledela

Answer:

The volume of mercury-contaminated water that has to be consumed to ingest 0.100 g mercury is 2.50 × 10⁴ l

Explanation:

Hi there!

First, let´s convert 0.100 g to mg:

0.100 g · (1000 mg/1 g) = 100 mg

The contaminated water has 0.004 mg per liter, then, we have to find the volume of water that contains 100 mg of mercury:

100 mg · (1 l / 0.004 mg) = 2.50 × 10⁴ l

Then, the volume of mercury-contaminated water ( at a concentration of 0.004 mg/l) that has to be consumed to ingest 0.100 g mercury is 2.50 × 10⁴ l

Have a nice day!

8 0
2 years ago
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