In the reaction 2Mg + O2 -> 2MgO (Mg = 24, MgO = 40 g/mol), what mass of MgO forms from 6 g of magnesium?
Answer and explanation
Correct answer: A. 10 g
- Step 1: Moles of Mg = 6 / 24 = 0.25 mol, and 2 mol Mg gives 2 mol MgO.
- Step 2: Mass of MgO = 0.25 x 40 = 10 g.
Answer
10 g.
Why not the others: '6 g' assumes the product has the same mass as the metal; '22 g' adds a single oxygen atom's mass to the metal; '3.6 g' inverts the mass ratio.
Practise more Chemical Energetics, Equilibrium and Organic Chemistry.
Free questions with an explanation for every one, and full timed Qatar Senior Secondary Certificate (Thanaweya) mock tests.
More Chemical Energetics, Equilibrium and Organic Chemistry questions
- Calculate the standard enthalpy of reaction Delta H°_rxn for the combustion of methane: CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l), given standard…
- For a reversible reaction at 298 K, Delta H° = -50 kJ/mol and Delta S° = -100 J/(mol*K). At what temperature does the reaction transition fr…
- For the gas-phase equilibrium N2O4(g) <=> 2NO2(g), the equilibrium constant K_p = 0.15 at 298 K. What is the value of K_c for this reaction?…
- What is the pH of a 0.050 M aqueous solution of barium hydroxide, Ba(OH)2, assuming complete dissociation at 25 °C?
- What is the molar solubility of silver chloride (AgCl) in pure water at 25 °C if its solubility product constant K_sp = 1.8 * 10^(-10)?
- Which of the following organic functional group tests produces a silver mirror on the inner glass wall of a test tube upon reaction with ald…