On one pan of the beam balance there is 0.5 mol of sodium hydroxide NaOH. How much copper sulfate CuSO4 should be put on the other pan to balance the balance?
n (NaOH) = 0.5 mol
m (CuSO4) -?
1) Using the periodic system of D.I.Mendeleev, calculate the molar mass of sodium hydroxide:
M (NaOH) = Mr (NaOH) = Ar (Na) * N (Na) + Ar (O) * N (O) + Ar (H) * N (H) = 23 * 1 + 16 * 1 + 1 * 1 = 40 g / mol;
2) Calculate the mass of sodium hydroxide:
m (NaOH) = n (NaOH) * M (NaOH) = 0.5 * 40 = 20 g;
3) To balance the scales, the masses of the substances must be equal. Means:
m (CuSO4) = m (NaOH) = 20 g.
Answer: The mass of copper sulfate is 20 g.
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