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3 years ago

What elements are being fused in a main sequence star?

Chemistry

1 answer:

mezya [45]3 years ago

7 0

Answer is: hydrogen (H).

Main sequence stars fuse hydrogen atoms to form helium atoms in their cores.

About 90 percent of the stars in the universe are main sequence stars.

Nuclear reaction is in the inner core of the Sun and hydrogen is conveted into helium.

The inner core is the central region of the Sun and all solar energy is produced in the core by nuclear fusion.

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Use the provided reduction potentials to calculate ArGº for the following balanced redox reaction: Pb2+(aq) + Cu(s) → Pb(s) + Cu

nydimaria [60]

Answer : The correct option is, +91 kJ/mole

Solution :

The balanced cell reaction will be,

$Cu(s)+Pb^{2+}(aq)\rightarrow Cu^{2+}(aq)+Pb(s)$

Here copper (Cu) undergoes oxidation by loss of electrons, thus act as anode. Lead (Pb) undergoes reduction by gain of electrons and thus act as cathode.

First we have to calculate the standard electrode potential of the cell.

$E^0_{[Pb^{2+}/Pb]}=-0.13V$

$E^0_{[Cu^{2+}/Cu]}=+0.34V$

$E^0_{cell}=E^0_{cathode}-E^0_{anode}$

$E^0_{cell}=E^0_{[Pb^{2+}/Pb]}-E^0_{[Cu^{2+}/Cu]}$

$E^0_{cell}=-0.13V-(0.34V)=-0.47V$

Now we have to calculate the standard Gibbs free energy.

Formula used :

$\Delta G^o=-nFE^o_{cell}$

where,

$\Delta G^o$ = standard Gibbs free energy = ?

n = number of electrons = 2

F = Faraday constant = 96500 C/mole

$E^o$ = standard e.m.f of cell = -0.47 V

Now put all the given values in this formula, we get the Gibbs free energy.

$\Delta G^o=-(2\times 96500\times (-0.47))=+90710J/mole=+90.71kJ/mole\approx +91kJ/mole$

Therefore, the standard Gibbs free energy is +91 kJ/mole

6 0

3 years ago

The molar heat of vaporization of water is 40.7kJ/mol. How much heat must be absorbed to convert 50.0 grams of liquid water at 1

EleoNora [17]

During a phase change the temperature does not change since all of the heat is being absorbed in order to break the intermolecular forces. Due to that, the formula will not need to have T in it and is actually q=nΔH(v).
n=the number of moles (in this case 2.778mol of water since you divide 50g by 18g/mol).
ΔH(v)=the molar heat of vaporization (in this case 40.7kJ/mol).
q=the heat that must be absorbed
q=2.778mol×40.7kJ/mol
q=113.1kJ
Therefore the water needs to absorb 1.13×10²kJ.

I hope this helps. Let me know if anything is unclear.

4 0

3 years ago

Peut-on être exact sans être précis?

Evgesh-ka [11]

Answer:

I think you can.

8 0

3 years ago

PLZZZZZZZZ HELPPPPPP<br>

hjlf

Answer:

482