Explanation:
thermal changes are those in which heat exchange is involved like endothermic and exothermic
while in chemical changes collision between the reactant occurs which result into product
<u>Answer:</u> The number of molecules of ethinyl estradiol present in one pill are 
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
Given mass of ethinyl estradiol = 0.038 mg = 
(Conversion factor: 1 g = 1000 mg)
Molar mass of ethinyl estradiol ![(C_{20}H_{24}O_2)=[(20\times 12)+(24\times 1)+(2\times 16)]=296g/mol](https://tex.z-dn.net/?f=%28C_%7B20%7DH_%7B24%7DO_2%29%3D%5B%2820%5Ctimes%2012%29%2B%2824%5Ctimes%201%29%2B%282%5Ctimes%2016%29%5D%3D296g%2Fmol)
Putting values in above equation, we get:
According to mole concept:
1 mole of a compound contains 
number of molecules
So, 
of ethinyl estradiol will contain = 
number of molecules
Hence, the number of molecules of ethinyl estradiol present in one pill are
The molar enthalpy of combustion in kj/mol of magnesium is 620 kj/mol, Option D is the correct answer.
<h3>What is enthalpy of Combustion ?</h3>
The energy released when a fuel is oxidized by an oxidizing agent is called enthalpy of Combustion.
It is given that
a 1.0 g sample of magnesium is burned to form MgO. in doing so, 25.5 kj of energy are released.
Molecular weight of Magnesium = 24.35g
24.35 g makes 1 mole of Mg
1g = 1/24.35
For 0.04 moles 25.5 kJ is released
for 1 mole 25.5 *1/.04
= 620 kj/mol
Therefore the molar enthalpy of combustion in kj/mol of magnesium is 620 kj/mol.
To know more about enthalpy of combustion
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The type of solvent that is needed to remove an oil stain would be an organic solvent. This is would dissolve the oil from the fabric to the solvent. Oil is nonpolar which would have the same polarity of an organic solvent. Hope this answers the question. Have a nice day.
Potassium and Nitrate ions are spectator ions in the reaction:
→ 
<h3>What are spectator ions?</h3>
Ions that are not involved in the actual chemical reaction are called spectator ions.
A precipitation reaction occurs when two ionic compounds react to produce a precipitate and an insoluble substance which stays in the solution as a spectator ion.
Hence, Potassium and Nitrate ions are spectator ions in the reaction:
→
Learn more about the spectator ions here:
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