How is an electromagnet different from a bar magnet?

A) Bar magnets have a north and south pole, but electromagnets do not.

B) Electromagnets are strong, permanent magnets, but bar magnets are always weaker.

C) Electromagnets are only magnetized when a current flows through a wire wrapped around the core.

Eliminate

D) Bar magnets are attracted to ferromagnetic substances such as iron. Electromagnets are attracted to all metals.

C) Electromagnets are only magnetized when a current flows through a wire wrapped around the core.

Explanation:

An electromagnet is a magnet that runs on electricity. Unlike a permanent magnet (bar magnet), amount of electric current that flows through electromagnet changes the strength of an electromagnet. The poles of an electromagnet are determined by flow of electricity.

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2