Question

Two basic laws of chemistry are the law of conservation of mass and the law of constant composition. Which of these laws (if any) do the following statements illustrate? (a) The mass of phosphorus, \(\mathrm{P},\) combined with one gram of hydrogen, \(\mathrm{H},\) in the highly toxic gas phosphene, \(\mathrm{PH}_{3}\), is a little more than twice the mass of nitrogen, \(\mathrm{N},\) combined with one gram of hydrogen in ammonia gas, \(\mathrm{NH}_{3}\). (b) A cold pack has the same mass before and after the seal between two reactants is broken to allow reaction to occur. (c) It is highly improbable that carbon monoxide gas found in Los Angeles is \(\mathrm{C}_{1.2} \mathrm{O}_{1.1}\).

Short answer

a) The mass of phosphorus combined with one gram of hydrogen in phosphene is a little more than twice the mass of nitrogen combined with one gram of hydrogen in ammonia gas. b) A cold pack has the same mass before and after the seal between two reactants is broken to allow the reaction to occur. c) It is highly improbable that carbon monoxide gas found in Los Angeles is C₁.₂O₁.₁. Answer: a) The law of constant composition b) The law of conservation of mass c) The law of constant composition

Step-by-step solution

Statement (a)

Let's analyze the first statement: "The mass of phosphorus, P, combined with one gram of hydrogen, H, in the highly toxic gas phosphene, \(\mathrm{PH}_{3}\), is a little more than twice the mass of nitrogen, N, combined with one gram of hydrogen in ammonia gas, \(\mathrm{NH}_{3}\)." This statement is comparing the masses of elements combined with hydrogen in two different compounds, phosphene and ammonia. This reflects the law of constant composition, which states that a given compound always contains elements in a fixed proportion by mass. Therefore, statement (a) illustrates the law of constant composition.

Statement (b)

Now let's analyze statement (b): "A cold pack has the same mass before and after the seal between two reactants is broken to allow the reaction to occur." In this situation, the mass of the system (cold pack) remains unchanged before and after the reaction takes place. This is an example of the law of conservation of mass, which states that mass cannot be created or destroyed during a chemical reaction. Therefore, statement (b) illustrates the law of conservation of mass.

Statement (c)

Finally, let's analyze statement (c): "It is highly improbable that carbon monoxide gas found in Los Angeles is \(\mathrm{C}_{1.2} \mathrm{O}_{1.1}\)." The given formula for carbon monoxide, \(\mathrm{C}_{1.2} \mathrm{O}_{1.1}\), features non-integral subscripts, which means it doesn't adhere to the fixed proportion of elements by mass in a compound. This inconsistency with the proper formula of carbon monoxide, \(\mathrm{CO}\), goes against the law of constant composition. Therefore, statement (c) illustrates the law of constant composition.