When a penny, which is mostly made of copper plated with a thin layer of zinc, is treated with muriatic acid (hydrochloric acid), the zinc layer dissolves, leaving only the copper core. The weight of the penny would decrease after the zinc layer is dissolved.
The weight of a U.S. penny before dissolving the zinc is approximately 2.5 grams. The weight of the zinc layer on a penny is about 2.5% of the total weight, while the copper core makes up the remaining 97.5%.
After dissolving the zinc layer with muriatic acid, the weight of the penny would be reduced by the weight of the dissolved zinc layer, which is about 2.5% of the original weight. Therefore, the weight of the penny after dissolving the zinc would be approximately 97.5% of the original weight, which is around 2.4375 grams.
Please note that actual results may vary slightly due to the specific composition of the penny and the effectiveness of the acid treatment.
