Question

compare the total mass of the reactants to the total mass of the products.
what choice demonstrates the law of conservation of mass?
$33\ce{n_{2}} + 28\ce{o_{2}} + 19\ce{h_{2}o} \
ightarrow 92\ce{nh_{4}no_{3}}$
$2\ce{g h_{2}} + 71\ce{g cl_{2}} \
ightarrow 91\ce{g hcl}$
$48\ce{g nacl} \
ightarrow 12\ce{g na} + 35\ce{g cl_{2}}$
$12\ce{g cl_{2}} + 13\ce{g k} \
ightarrow 25\ce{g kcl}$

Explanation:

Step1: Calculate reactant mass (1)

$33 + 28 + 19 = 80$; $92$ (products)

Step2: Calculate reactant mass (2)

$2 + 71 = 73$; $91$ (products)

Step3: Calculate reactant mass (3)

$48$ (reactant); $12 + 35 = 47$ (products)

Step4: Calculate reactant mass (4)

$12 + 13 = 25$; $25$ (products)

Answer:

12 g Cl₂ + 13 g K → 25 g KCl