Question

law of conservation of mass experiment
material(s) mass (g)
mass of test tube 42.78
mass of steel wool 0.70
mass of steel wool & test tube (original) 43.48
mass of steel wool & test tube (after burning) ?
students conduct an experiment in which steel wool is burned in a closed test tube. the steel wool reacts with an amount of oxygen equal to 1.48% of the mass of the steel wool. what is the correct value for the missing mass in the table?
a 0.71 g
b 42.78 g
c 43.48 g
d 44.20 g

Explanation:

Step1: Calculate mass of oxygen reacted

The mass of steel wool is $0.70$ g. The mass of oxygen that reacts is $1.48\%$ of the mass of steel wool. So, mass of oxygen $=0.70\times\frac{1.48}{100}=0.70\times0.0148 = 0.01036$ g.

Step2: Apply law of conservation of mass

In a closed - system (the closed test - tube), the total mass before the reaction is equal to the total mass after the reaction. The total mass before the reaction is the mass of steel wool and test - tube which is $43.48$ g. After the reaction, the steel wool reacts with oxygen, but the total mass of the closed - system remains the same.

Answer:

C. $43.48$ g