Question detail
Given the balanced equation 2H2 + O2 → 2H2O, how many oxygen atoms are involved in the reaction? Justify your answer using the equation.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations
Question
Given the balanced equation 2H2 + O2 → 2H2O, how many oxygen atoms are involved in the reaction? Justify your answer using the equation.
Answer
In the reaction, there is 1 O2 molecule, which contains 2 oxygen atoms. This is justified by noting that the subscript '2' in O2 indicates that there are two oxygen atoms in that molecule.
Explanation
This question assesses the student's ability to interpret subscripts in a balanced equation to count atoms. A strong answer correctly identifies the number of oxygen atoms and provides justification based on the equation.
Common mistake
Misinterpreting Subscripts
Students often confuse subscripts in chemical formulae with multipliers, leading to incorrect counting of atoms in balanced equations.
To fix this, students should remember that subscripts indicate the number of atoms of an element in a molecule, while multipliers apply to the entire formula. Practice identifying and counting atoms using examples. Keep the correction anchored to Conservation of mass and balanced chemical equations; check formula, substitution, calculation, final answer, and unit where relevant.
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