Answer:
35 grams of oxygen
Step-by-step explanation:
The law of constant proportion or composition states that the elements that combine to form a chemical compound combine in fixed whole number ratios.
Therefore, the ratio of the that make up any pure sample of a given compound are present in the same mass ratio
The given parameters are;
The mass of oxygen that reacts completely with 100 grams of copper, (cu) = 25.0 grams
Therefore;
1 gram of copper completely reacts with 25/100 = 1/4 grams of oxygen
140 grams of copper will completely react with 140 × 1/4 = 35 grams of oxygen
∴ 35 grams of oxygen will completely react with 140grams of copper.