What volume of oxygen will remain after reacting 8cm3 of hydrogen with 20cm3 of oxygen?

This question is about a chemical reaction between hydrogen and oxygen. The reaction produces water and releases energy in the form of heat and light. Since oxygen is in excess in this reaction, it won't be completely used up, so the question asks how much oxygen will remain after the reaction. To solve the problem, we need to balance the chemical equation for the reaction and then use stoichiometry to calculate the amount of oxygen used up. The balanced chemical equation for the reaction is: 2H2 + O2 → 2H2O From the equation, we can see that 2 moles of hydrogen react with 1 mole of oxygen to produce 2 moles of water. Therefore, if 8 cm³ of hydrogen is reacted, it would require half the amount (i.e., 4 cm³) of oxygen. However, since the question asks for the amount of oxygen remaining, we need to subtract the amount used up from the initial amount of oxygen given (i.e., 20 cm³). Therefore, the answer is: 20 cm³ - 4 cm³ = 16 cm³ Therefore, the correct answer is "16 cm³".