Question

Caren combines copper (Cu) and silver nitrate, (AgNO3) producing copper nitrate (Cu(NO3)2) and silver (Ag), as shown in the chemical equation.

Cu + 2AgNO3 → Cu(NO3)2 + 2Ag

She records the total mass of copper and silver nitrate in the lab before combining them. The table shows her measurements.


Substances Mass (g)
copper and silver nitrate 64
copper nitrate and silver ?

Caren predicts that the mass of the products will be 76 g. According to the law of conservation of matter, is Caren's prediction reasonable? Why or why not?

a
Her prediction is unreasonable because the law of conservation of matter states that some mass is lost in a chemical reaction, so the mass of the products will be less than 64 g.
b
Her prediction is unreasonable because the law of conservation of matter states that matter can neither be created nor destroyed, so the mass of the products will be 64 g.
c
Her prediction is reasonable because the law of conservation of matter states that matter can neither be created nor destroyed in a chemical reaction.
d
Her prediction is reasonable because the law of conservation of matter states that the products of a reaction have more mass than the reactants.

Answer 1

Answer: b

Caren's prediction is unreasonable. By the law of conservation of matter (mass), in a closed system the total mass of the products equals the total mass of the reactants, so the products should have mass 64 g, not 76 g.