35 cm3 of oxygen is made to react with 50 cm3 of hydrogen, and the whole reaction mixture was then passed through anhydrous calcium chloride. What is the volume of gas left?

Here are the explanations for the two incorrect answers:

: Reaction of Oxygen and Hydrogen

Question: $35\text{ cm}^3$ of oxygen is made to react with $50\text{ cm}^3$ of hydrogen, and the whole reaction mixture was then passed through anhydrous calcium chloride. What is the volume of gas left?
Your Answer: $5\text{ cm}^3$.
Correct Answer: $75\text{ cm}^3$.

Step 1: Write the balanced chemical equation for the reaction.
Hydrogen and oxygen react to form water:

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