Which of the following reactions represents a precipitation reaction? A. CoCl2(aq) + Na, so,(aq) → Coso (aq)+2NaCl(aq)
B. AgNO, (aq) + KCI (aq) → AgCl (s) + KNO3(aq)
C. HNO3(aq) + NaF(aq) → HF(aq) + NaNO3(aq)
D. AgNO3(aq) + NaCl (s) → AgCl (aq) + NaNO3(aq)

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.