Which of the following is a way in which elements and compounds are similar?

Elements and compounds are listed on the periodic table.

Elements and compounds are pure substances.

Elements and compounds are both made up of different kinds of atoms.

Elements and compounds can both be broken down by physical means.

Elements and compounds are pure substances.

Elements are formed by just one kind of atoms (Na, Fe, H₂, O₃), while compounds are formed by 2 or more kinds of atoms (H₂O, NaCl, CO₂).

Which of the following is a way in which elements and compounds are similar?

All in all, elements and compounds are pure substances is the correct choice.

You can learn more about elements and compounds here: link

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

a is the correct answer