Question

Какая масса раствора с массовой долей гидроксида калия 24% потребуется для полной нейтрализации раствора соляной кислоты массой 40 г с массовой долей растворённого вещества 30%? При нахождении количества молей ответ округлить до сотых, а в остальных случаях — до целых.

Answer 1

Масса соляной кислоты:
40 г * 0,3 = 12 г
Уравнение реакции:
х г         12 г
KOH + HCl = KCl + H₂O
56 г/м 36,5 г/м

х = 56*12/36,5
х = 18,41

Масса чистого гидроксида калия равна 18,41 г. По условию задачи, KOH находится в растворе, его концентрация = 24%, следовательно масса раствора равна
18,41 г / 0,24 = 76,7 г
Ответ: 76,7 г.

Answer 2

Calculation of the Mass of Potassium Hydroxide Solution Needed for Neutralization

To calculate the mass of potassium hydroxide (KOH) solution needed to neutralize the hydrochloric acid (HCl) solution, we can use the following steps:

1. Determine the number of moles of HCl in the given mass of the solution. 2. Use the balanced chemical equation for the neutralization reaction between HCl and KOH to determine the stoichiometric ratio. 3. Calculate the number of moles of KOH required for neutralization. 4. Convert the moles of KOH to the mass of KOH solution using the concentration of KOH.

Let's proceed with the calculations:

Step 1: Calculate the number of moles of HCl in the given mass of the solution. - The mass of the hydrochloric acid solution is given as 40 g. - The mass fraction of the dissolved substance (HCl) is given as 30%.

To calculate the mass of HCl in the solution, we multiply the mass of the solution by the mass fraction of HCl: Mass of HCl = 40 g * 0.30 = 12 g.

To calculate the number of moles of HCl, we divide the mass of HCl by its molar mass: Number of moles of HCl = 12 g / 36.46 g/mol = 0.329 mol (rounded to three decimal places).

Step 2: Use the balanced chemical equation to determine the stoichiometric ratio. The balanced chemical equation for the neutralization reaction between HCl and KOH is: HCl + KOH → H2O + KCl.

From the balanced equation, we can see that the stoichiometric ratio between HCl and KOH is 1:1.

Step 3: Calculate the number of moles of KOH required for neutralization. Since the stoichiometric ratio between HCl and KOH is 1:1, the number of moles of KOH required for neutralization is also 0.329 mol.

Step 4: Convert the moles of KOH to the mass of KOH solution using the concentration of KOH. - The mass fraction of KOH in the solution is given as 24%. - The molar mass of KOH is 56.11 g/mol.

To calculate the mass of KOH solution, we can use the following formula: Mass of KOH solution = (Number of moles of KOH) * (Molar mass of KOH) / (Mass fraction of KOH).

Substituting the values: Mass of KOH solution = (0.329 mol) * (56.11 g/mol) / (0.24) = 76.45 g (rounded to two decimal places).

Therefore, the mass of the potassium hydroxide solution with a mass fraction of 24% required for the complete neutralization of the hydrochloric acid solution with a mass of 40 g and a mass fraction of 30% is approximately 76.45 g.