Some iron wire weighing 5.6 g is placed in a beaker and covered with 15.0 g of dilute hydrochloric acid. The acid reacts with the metal and gives off hydrogen gas, which escapes into the surrounding air. After reaction, the contents of the beaker weighs 20.4 g. What is the mass of hydrogen gas produced by the reaction?
Solution:
We can use the law of conservation of mass to figure out the mass of hydrogen gas produced. We can write the following:
Mass of iron + mass of hydrochloric acid = mass of conents of beaker + mass of hydrogen
Thus, we can write:
5.6g+15.0g=20.4g+m_H
m_H=0.2g
This question can be found in General Chemistry, 9th edition, chapter 1, question 1.38
