Answer:
20%
Step-by-step explanation:
a) The purpose of the experiment was likely to investigate the reaction between the heated copper and air within the combustion tube.
b) The volume of air decreased due to a chemical reaction taking place between the copper and the oxygen in the air. This reaction consumed some of the oxygen, resulting in a reduction in volume.
c) The observations in the combustion tube during the experiment would depend on the specific reaction that took place. Generally, one would expect to observe changes in color, temperature, and possibly the formation of new compounds or substances. Without further information, it is difficult to provide specific details.
d) The equation for the reaction that took place would depend on the specific reaction between the copper and oxygen. However, a general equation for the reaction between copper and oxygen can be represented as:
2Cu + O2 -> 2CuO
This equation represents the formation of copper(II) oxide (CuO) when copper (Cu) reacts with oxygen (O2).
e) To calculate the percentage of gas used during the experiment, we can use the initial and final volumes of air passed through the combustion tube.
Initial volume = 80 cm³
Final volume = 64 cm³
The difference in volume represents the gas used during the experiment:
Gas used = Initial volume - Final volume
= 80 cm³ - 64 cm³
= 16 cm³
To calculate the percentage of gas used, we need to find the ratio of gas used to the initial volume, and then multiply by 100:
Percentage of gas used = (Gas used / Initial volume) * 100
= (16 cm³ / 80 cm³) * 100
= 20%
Therefore, the percentage of gas used during the experiment is 20%.