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castortr0y [4]
3 years ago
10

Since helium is lighter than air, it is difficult to measure the mass of a sample, so to find out the mass of helium in a birthd

ay balloon, a student transferred the helium to a fixed 1.50 L vessel at 25.0 °C and found the pressure to be 3.04 atm. What mass of helium is in the balloon?
Chemistry
1 answer:
d1i1m1o1n [39]3 years ago
6 0

Answer:

0.7457 g is the mass of the helium gas.

Explanation:

Given:  

Pressure = 3.04 atm

Temperature = 25.0 °C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15  

So,  

T₁ = (25.0 + 273.15) K = 298.15 K  

Volume = 1.50 L

Using ideal gas equation as:

PV=nRT

where,  

P is the pressure

V is the volume

n is the number of moles

T is the temperature  

R is Gas constant having value = 0.0821 L.atm/K.mol

Applying the equation as:

3.04 atm × 1.50 L = n × 0.0821 L.atm/K.mol × 298.15 K  

<u>⇒n = 0.1863 moles</u>

Molar mass of helium = 4.0026 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

0.1863\ mole= \frac{Mass}{4.0026\ g/mol}

Mass_{He}= 0.7457\ g

<u>0.7457 g is the mass of the helium gas. </u>

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steposvetlana [31]

Answer: Niels Bohr - Drew first picture of atom

n=1 shell - inner orbit

electron - Negative charge

Electron cloud - 3D orbits

Proton - postive charge

Molecule - two or more atoms bonded

Orbit - electron path

John Dalton - Develope atomic theory

Explanation:

1. Niels Borh proposed an atom model taking into account quantum physics. In his model, he proposed that electrons orbit around the nucleus in limited areas and if they need energy to move between orbitals. Although this model has been modified according to recent discoveries, basic postulates remain, that is why is so important the Borh's model

2. n is the principal quantum number which correspond to the orbital of and atom. According to Bohr's model orbits are organized depending on the energy, obits with lower energy are closer to the nucleus and have lower quantum number, so n=1 represent the orbit which closer to the nucleus

3. An electron is a particle of the atom, is the smallest of them and it has negative charge that are attracted by the positive charge of protons, that is why they are orbiting the nucleus.  

4. In modern model there is a principle of uncertainty that states that we can not know the speed and the position of an electron at the same time, so the orbits are consider as spaces or regions where is probable to find and electron. This regions are three dimentional as we conceive the world so they are compare to a cloud with negative charge

5. proton is the partice located in the nucleus of the atom. It was discovered by Rutherford who realized that this particles were attracted to negative charges, and takin into account that different charges attract each other, he concluded that protons have positive charge

6. molecules are the elemental part of a compound and they are made by the two or more atoms that bond through electrons

7 atom is the basic unit of matter because it has particular characteristics according to the number of protons and electrons. This units built all things known in the universe.

8. An orbit was consider by Borh as the path that the electron follows in order to remain closer to the nucleus. He proposed that is was a straigh path as the planets arroud the sun, but nowdays we know that elelctrons are considered in a 3D space that move arround the nucleus.

9. John Dalton is the scientist in modern era that proposed the existence of atoms after studing greek philosophers writings about matter. He proposed that atoms were the smallest unit of matter and the make all the things in nature. Acoording to him, the nature of the electron and the size of it made the diferent elements in the universe. His postulates are very important in science because open a new are of research for chemists and physicists

8 0
3 years ago
Many portable gas heaters and grills use propane, C3H8(g). Using enthalpies of formation, calculate the quantity of heat produce
Elodia [21]

Answer:  600 kJ

-

Explanation:

                        C₃H₈ (g)  + 5 O₂ (g) =============== 3 CO₂ (g)  +  4 H₂O (l)

Δ⁰Hf   kJ/mol       -104             0                                       -393.5         -285.8

Δ⁰Hcomb C₃H₈ = 3(-393.5) + 4 (-285.80) - (-104)  kJ/mol

Δ⁰Hcomb = 2219.70 kJ/mol

n= m /MW   MW c₃H₈ = 44.1 g/mol

n= 12 g/44.1 g/mol = 0.27 mol

then for 12 g the heat released will be

0.27 mol x 2219.70 kJ/mol =  600 KJ

4 0
3 years ago
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il63 [147K]
True :)

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3 years ago
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Which change happens when a fan is turned on?
fgiga [73]

Answer:

D. Electrical energy is changed into mechanical energy

Explanation:

When you turn on the fan, the electricity that is given through the power outlet allows the fan to have the available energy to spins the fan blades. By the fan's blades spinning, this is a movement that can be described as mechanical energy.

7 0
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babunello [35]

Answer:

B

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