Question

В лабораторию для анализа поступил образец технического нитрата меди(II). Образец массой 7,52 г поместили в мерную колбу на 100 мл, и довели дистиллированной водой до метки. Затем отобрали аликвоту в 10 мл, добавили избыток раствора йодида калия и оставили в тёмном месте на 10 минут. После этого оттитровали свежеприготовленным раствором тиосульфата натрия с использованием крахмала. На титрование потребовалось 6 мл 0,5 М раствора тиосульфата. Рассчитайте содержание (в %) нитрата меди(II). В ответ запишите число, округлив его до целого значения. При расчётах примите молярную массу меди равной 64 г/моль.​

Answer 1

m р-ра =376 г

надо найти массу Cu(NO3)2= w Cu(NO3)2*m р-ра = 0.075*376=28.2 г

28.2 x

Cu(NO3)2+2KOH=Cu(OH)2↓+2KNO3

188 98

x=98г*28,2г/188г=14,7г

Answer 2

Calculation of Copper Nitrate (II) Content

To calculate the percentage of copper nitrate (II) in the given sample, we need to determine the number of moles of thiosulfate used in the titration.

First, let's calculate the number of moles of thiosulfate used in the titration. We know that 6 mL of a 0.5 M solution of thiosulfate was required for the titration.

The equation for the reaction between copper nitrate (II) and thiosulfate is as follows:

Cu(NO3)2 + 2Na2S2O3 → CuS2O3 + 2NaNO3

From the balanced equation, we can see that 1 mole of copper nitrate (II) reacts with 2 moles of thiosulfate. Therefore, the number of moles of thiosulfate used can be calculated as follows:

Number of moles of thiosulfate = (Volume of thiosulfate used in titration) × (Molarity of thiosulfate) Number of moles of thiosulfate = 6 mL × 0.5 mol/L Number of moles of thiosulfate = 0.003 mol

Next, let's calculate the number of moles of copper nitrate (II) in the 10 mL aliquot. Since the ratio of copper nitrate (II) to thiosulfate is 1:2, the number of moles of copper nitrate (II) is half the number of moles of thiosulfate used in the titration:

Number of moles of copper nitrate (II) = 0.003 mol / 2 Number of moles of copper nitrate (II) = 0.0015 mol

Now, let's calculate the mass of copper nitrate (II) in the 10 mL aliquot. We can use the molar mass of copper (64 g/mol) to convert moles to grams:

Mass of copper nitrate (II) = Number of moles of copper nitrate (II) × Molar mass of copper Mass of copper nitrate (II) = 0.0015 mol × 64 g/mol Mass of copper nitrate (II) = 0.096 g

Since the 10 mL aliquot was taken from a 100 mL solution, the mass of copper nitrate (II) in the original solution can be calculated by proportion:

Mass of copper nitrate (II) in original solution = (Mass of copper nitrate (II) in 10 mL aliquot) × (Total volume of solution / Volume of aliquot) Mass of copper nitrate (II) in original solution = 0.096 g × (100 mL / 10 mL) Mass of copper nitrate (II) in original solution = 0.96 g

Finally, let's calculate the percentage of copper nitrate (II) in the original sample:

Percentage of copper nitrate (II) = (Mass of copper nitrate (II) / Mass of original sample) × 100% Percentage of copper nitrate (II) = (0.96 g / 7.52 g) × 100% Percentage of copper nitrate (II) ≈ 12.77%

Therefore, the percentage of copper nitrate (II) in the sample is approximately 12%.

Please note that the molar mass of copper used in the calculation is assumed to be 64 g/mol.