Answer:-A. It is less than 890 kJ/mol because the amount of energy required to break bonds is less than the amount of energy released in forming bonds.
Explanation: Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and 
for the reaction comes out to be positive.
Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and for the reaction comes out to be negative.
In the formation of new bonds more energy is released than is required to break the existing bonds, heat is released.
In the formation of bonds less energy is released than is required to break the existing bonds, heat is absorbed.
Magnetic reversals
Explanation:
A change in the orientation of the earth's magnetic field is known as magnetic reversals.
During a magnetic reversal, the geographic south pole aligns with the magnetic north.
The geographic north pole aligns with the magnetic south.
- The geomagnetic field of the earth is produced by the movement of metallic minerals in the outer core.
- This streaming of metallic minerals generals electric current that induces a magnetic field.
learn more:
Sea floor spreading brainly.com/question/12037536
#learnwithBrainly
Answer:
The answer to your question is: 0.05 M
Explanation:
I'm not sure about the units umol, I think is units mol.
Data
MgF2 = 0.0191 mol
Volume = 400 ml
Molarity = moles / volume
Molarity = 0.0191 / 0.4 l
Molarity = 0.048 ≈ 0.05 M
