Question

In an experiment the following reactions take place:
X + Y → Z

2 g 4 g u g

Z + A→ B

u g 7 g c g

What is the value of u and c respectively?

• A. 4.8 g
• B. 1.2 g
• C. 2.4 g
• D. 9.8 g

Answer 1

The correct option is

D

2.4 g

According to the law of conservation of mass, the total mass of reactants is equal to the total mass of products.

For,
X + Y → Z

2 g 4 g u g

Mass of Z = Mass of X + Mass of Y
⇒ u = (2+4) g = 6 g

Similarly for,
Z + A→ B

u g 7 g c g

Mass of B = Mass of A + Mass of Z
⇒ c = (u+7) g = (6+7) g = 13 g.
Hence, the mass of Z= 6 g and mass of B = 13 g.