An element M forms a hydride MH3 which contains 90% of M by mass. What is the relative atomic mass of M?
Correct answer: A. 27
- A. 27
- B. 30
- C. 87
- D. 90
Explanation
To calculate the relative atomic mass of M, we can use the fact that the hydride MH3 contains 90% of M by mass.Let the atomic mass of M be x. Then, the mass of M in one molecule of MH3 is x/3, and the mass of H in one molecule of MH3 is (3 x 1.008) = 3.024.Since the hydride MH3 contains 90% of M by mass, we can write:mass of M in MH3 / total mass of MH3 = 0.9(x/3) / (x/3 + 3.024) = 0.9Solving this equation, we get x = 27. Therefore, the relative atomic mass of M is 27.
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Mole calculations connect mass, number of particles and Avogadro's number, while balanced equations provide the mole ratios used in stoichiometry. Questions cover limiting and excess reactants, theoretical yield and percentage yield, including identifying which reactant is consumed first and comparing the actual product with the maximum possible product.
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