Question

СРОЧНО, ПОЖАЛУЙСТА ОЧЕНЬ СРОЧНО!!!!!!!При добавлении к раствору гидроксида натрия с массовой долей 10% избытка раствора сульфата меди 2 образовался осадок массой 4,9 г. Опредилите массу исходного раствора щёлачи

Answer 1

2NaOH + CuSO4 --> Na2SO4 + Cu(OH)2
n(Cu(OH)2)= 4.9/98 = 0.05 моль
n(NaOH) = 2n(Cu(OH)2) = 0.1 моль
m(NaOH)= M*n = 40 * 0.1 = 4г
m(NaOH)p-p=m(NaOH)/10 * 100 = 4/10 * 100 = 40г 

Answer 2

Calculation of the Mass of the Original Solution of Sodium Hydroxide

To determine the mass of the original solution of sodium hydroxide (NaOH), we need to use the information provided. According to the question, a solution of sodium hydroxide with a mass fraction of 10% was added to an excess amount of copper sulfate (CuSO4) solution, resulting in the formation of a precipitate weighing 4.9 grams.

To solve this problem, we can use the concept of stoichiometry and the balanced chemical equation for the reaction between sodium hydroxide and copper sulfate:

2NaOH + CuSO4 -> Na2SO4 + Cu(OH)2

From the balanced equation, we can see that 2 moles of sodium hydroxide react with 1 mole of copper sulfate to produce 1 mole of copper hydroxide. We can use this information to calculate the number of moles of copper hydroxide formed.

The molar mass of copper hydroxide (Cu(OH)2) is: 1 atom of copper (Cu) = 63.55 g/mol 2 atoms of oxygen (O) = 2 * 16.00 g/mol = 32.00 g/mol 2 atoms of hydrogen (H) = 2 * 1.01 g/mol = 2.02 g/mol

Total molar mass of Cu(OH)2 = 63.55 + 32.00 + 2.02 = 97.57 g/mol

Using the given mass of the precipitate (4.9 g) and the molar mass of Cu(OH)2, we can calculate the number of moles of Cu(OH)2 formed:

Number of moles of Cu(OH)2 = Mass of Cu(OH)2 / Molar mass of Cu(OH)2 Number of moles of Cu(OH)2 = 4.9 g / 97.57 g/mol

Now, to find the number of moles of sodium hydroxide (NaOH) used in the reaction, we can use the stoichiometry of the balanced equation. Since 2 moles of NaOH react with 1 mole of CuSO4 to produce 1 mole of Cu(OH)2, the number of moles of NaOH used is half the number of moles of Cu(OH)2 formed:

Number of moles of NaOH = 1/2 * Number of moles of Cu(OH)2

Finally, to calculate the mass of the original solution of sodium hydroxide, we need to consider the mass fraction of NaOH in the solution. The mass fraction of NaOH is given as 10%, which means that 10 grams of NaOH are present in 100 grams of the solution.

Mass of the original solution of NaOH = (Number of moles of NaOH) * (Molar mass of NaOH) / (Mass fraction of NaOH)

Let's calculate the mass of the original solution of sodium hydroxide using the given information:

Step 1: Calculate the number of moles of Cu(OH)2 formed: Number of moles of Cu(OH)2 = 4.9 g / 97.57 g/mol

Step 2: Calculate the number of moles of NaOH used: Number of moles of NaOH = 1/2 * Number of moles of Cu(OH)2

Step 3: Calculate the mass of the original solution of NaOH: Mass of the original solution of NaOH = (Number of moles of NaOH) * (Molar mass of NaOH) / (Mass fraction of NaOH)

Now, let's perform the calculations:

Step 1: Calculate the number of moles of Cu(OH)2 formed: Number of moles of Cu(OH)2 = 4.9 g / 97.57 g/mol = 0.0502 mol

Step 2: Calculate the number of moles of NaOH used: Number of moles of NaOH = 1/2 * 0.0502 mol = 0.0251 mol

Step 3: Calculate the mass of the original solution of NaOH: Mass of the original solution of NaOH = (0.0251 mol) * (40.00 g/mol) / (0.10) = 10.025 g

Therefore, the mass of the original solution of sodium hydroxide (NaOH) is approximately 10.025 grams.

Please note that the calculations provided are based on the information given in the question.