Answer :
Option C) 2.5 units
Explanation : For calculating the strength of a unknown magnetic field in comparison with the given magnetic field we can use the magnetic formula as;
On substituting the values we get;
;
On solving we get the magnetic B field strength as
2.5 units
Answer: D. Electrostatic forces
Explanation:
The given question is incomplete. the complete question is:
The world burns the fossil fuel equivalent of approximately 
kg of petroleum per year. Assume that all of this petroleum is in the form of octane. Calculate how much CO2 in kilograms is produced by world fossil fuel combustion per year.( Hint: Begin by writing a balanced equation for the combustion of octane.)
Answer: 
Explanation:
Combustion is a chemical reaction in which hydrocarbons are burnt in the presence of oxygen to give carbon dioxide and water.
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
To calculate the moles :
According to stoichiometry :
As 2 moles of octane give = 16 moles of 
Thus 
of octane give =
of
Mass of 
Thus of is produced by world fossil fuel combustion per year.
The atomic radius of main group elements generally increases down a group because as there are more electrons they are farther away from the nucleus and the electrons closer to the nucleus shield the outer electrons from the protons for attraction.
