Question

на нейтрализацию 20г раствора NaOH затрачено 45г раствора соляной кислоты с массовой долей HСl 1.46%. Расчитайте массовую долю гидроксида натрия в исходном растворе

Answer 1

mHCl = 45*0,0146 = 0,657г

NaOH + HCl = NaCl + H2O

х          0,657г

40г       36,5г

mNaOH = 0,657*40\36,5 = 0,72г

wNaOH = 0,72\20 = 0,036 или 3,6%

 

Answer 2

Calculation of the Mass Fraction of Sodium Hydroxide in the Initial Solution

To calculate the mass fraction of sodium hydroxide (NaOH) in the initial solution, we need to use the balanced chemical equation for the neutralization reaction between sodium hydroxide and hydrochloric acid (HCl):

NaOH + HCl → NaCl + H2O From the equation, we can see that one mole of NaOH reacts with one mole of HCl to produce one mole of NaCl and one mole of water.

Given that 45 grams of hydrochloric acid solution with a mass fraction of HCl of 1.46% is used to neutralize 20 grams of sodium hydroxide solution, we can calculate the number of moles of HCl used:

Mass of HCl = Mass of HCl solution × Mass fraction of HCl Moles of HCl = Mass of HCl / Molar mass of HCl

The molar mass of HCl is approximately 36.46 g/mol.

Let's calculate the moles of HCl used:

Moles of HCl = (45 g × 0.0146) / 36.46 g/mol

Now, since the reaction is 1:1 between NaOH and HCl, the moles of NaOH used will be equal to the moles of HCl used.

Next, we can calculate the mass of NaOH in the initial solution:

Mass of NaOH = Moles of NaOH × Molar mass of NaOH

The molar mass of NaOH is approximately 39.997 g/mol.

Finally, we can calculate the mass fraction of NaOH in the initial solution:

Mass fraction of NaOH = Mass of NaOH / (Mass of NaOH + Mass of water)

Let's perform the calculations:

Moles of HCl = (45 g × 0.0146) / 36.46 g/mol

Mass of NaOH = Moles of HCl × Molar mass of NaOH

Mass fraction of NaOH = Mass of NaOH / (Mass of NaOH + Mass of water)

Please note that the molar mass values used here are approximate and may vary slightly depending on the source.