What mass of hydrogen gas was produced?  What mass of zinc reacted?  What was the percentage of zinc (by mass) in the alloy?
A sample of brass weighing 1.203 grams was analyzed. Brass is an alloy composed of copper, Cu, and zinc, Zn. The zinc in the alloy was reacted with 35.123 grams of hydrochloric acid, HCl, in excess, according to the following balanced equation:ÂÂ
Zn(s) + 2 HCl (aq) → H2 (g) + ZnCl2 (aq)ÂÂ
After all of the zinc reacted, the mass of the remaining solution weighed 36.309 grams. ÂÂ
What mass of hydrogen gas was produced? ÂÂ
What mass of zinc reacted? ÂÂ
What was the percentage of zinc (by mass) in the alloy?
The Correct Answer and Explanation is :
To determine the mass of hydrogen gas produced, the mass of zinc that reacted, and the percentage of zinc by mass in the brass alloy, we can follow these steps:
1. Calculate the Mass of Hydrogen Gas Produced:
he initial mass of the hydrochloric acid solution was 35.123 grams, and after the reaction, the mass of the remaining solution was 36.309 grams.he increase in mass is due to the addition of the zinc chloride formed during the reaction.ince the mass of the system is conserved and hydrogen gas escapes as a gas, the mass of the hydrogen gas produced is equal to the loss in mass of the system.
owever, in this case, the mass of the system increased, indicating that the mass of the hydrogen gas produced is negligible compared to the precision of the measurements.herefore, we can approximate the mass of hydrogen gas produced as zero.
2. Calculate the Mass of Zinc Reacted:
he balanced chemical equation for the reaction between zinc and hydrochloric acid is:
[ \text{Zn(s)} + 2\ \text{HCl(aq)} \rightarrow \text{H}_2\ \text{(g)} + \text{ZnCl}_2\ \text{(aq)} ]
rom the equation, one mole of zinc produces one mole of hydrogen gas.ince the mass of hydrogen gas produced is negligible, we can infer that the mass of zinc reacted is also negligible.
3. Calculate the Percentage of Zinc by Mass in the Alloy:
iven that the mass of zinc reacted is negligible, the percentage of zinc by mass in the brass alloy is approximately zero.
Explanation:
n this analysis, the negligible mass of hydrogen gas produced suggests that the amount of zinc in the brass sample is very small.rass is primarily composed of copper and zinc, and the negligible zinc content indicates that this particular sample is almost entirely copper.he precision of the measurements provided does not allow for the detection of such small quantities of zinc.
herefore, based on the given data, we conclude that the mass of hydrogen gas produced and the mass of zinc reacted are negligible, and the brass alloy consists almost entirely of copper.