Question

К колбе с 200 г воды добавили 6,9 г натрия. После окончания реакции к получившемуся раствору добавили 100 г раствора азотной кислоты с массовой долей кислоты 6,3%. Рассчитайте массовые доли всех веществ (в процентах) в конечном растворе.

Answer 1

Объяснение:

Уравнения протекающих реакций

2Na + 2H2O = 2NaOH + H2

NaOH + HNO3 = NaNO3 + H2O

По первой реакции образуется

n(Na)=6.9/23=0,3 моль n(Na)=n(NaOH)=0.3 моль

n(H2)=0.5n(Na) m(H2)=(0.3*0.5)=0.15 моль m(H2)=0.15*2=0.3 грамма

Во второй реакции гидрооксид натрия вступит в реакцию с азотной кислотой с образованием соли.

m(HNO3)=100*0.063=6,3 грамма n(HNO3)=6.3/63=0.1 моль

Азотная кислота полностью израсходуется т.к. в недостатке, при этом образуется соль и в растворе останется избыток гидрооксида натрия.

n(NaOH)=0.3-0.1=0.2 моль m(NaOH)=0.2*40=8 грамм

n(NaNO3)=n(HNO3)  m(NaNO3)=0.1*85=8.5 грамма

Итого имеем раствор общей массой 200 и 100 грамм, и минус 0,3 грамма водорода, улетевшего в результате реакции с натрием. Найдем массу раствора и массовые доли веществ

m(Sol)=200+100-0.3 =299,7 грамм

W(NaOH)=8/299.7=0,0266 - 2,66%

W(NаNO3)=8,5/299,7=0,0283 - 2,83%

Ответ: массовая доля гидрооксида натрия в растворе составит 2,66%, а нитрата натрия 2,83%.

 

Answer 2

Calculation of Mass Percentages in the Final Solution

To calculate the mass percentages of all substances in the final solution, we need to consider the initial solution containing water and sodium (Na), as well as the subsequent addition of nitric acid (HNO3).

Given information: - Mass of water (H2O) = 200 g - Mass of sodium (Na) added = 6.9 g - Mass of nitric acid solution added = 100 g - Mass fraction of acid in the nitric acid solution = 6.3%

To calculate the mass percentages, we will follow these steps:

1. Calculate the mass of water (H2O) remaining after the reaction with sodium (Na). 2. Calculate the mass of sodium hydroxide (NaOH) formed from the reaction between sodium (Na) and water (H2O). 3. Calculate the mass of nitric acid (HNO3) in the final solution. 4. Calculate the total mass of the final solution. 5. Calculate the mass percentages of each substance in the final solution.

Let's perform the calculations step by step.

Step 1: Calculate the mass of water remaining after the reaction

The reaction between sodium (Na) and water (H2O) can be represented as follows:

2Na + 2H2O -> 2NaOH + H2

Since the stoichiometric ratio between sodium (Na) and water (H2O) is 2:2, we can conclude that all the sodium (Na) reacts with water (H2O) to form sodium hydroxide (NaOH). Therefore, the mass of water remaining after the reaction is 0 g.

Step 2: Calculate the mass of sodium hydroxide formed

The molar mass of sodium hydroxide (NaOH) is 40 g/mol (Na: 23 g/mol, O: 16 g/mol, H: 1 g/mol).

Since the stoichiometric ratio between sodium (Na) and sodium hydroxide (NaOH) is 2:2, we can conclude that the mass of sodium hydroxide formed is equal to the mass of sodium (Na) added, which is 6.9 g.

Step 3: Calculate the mass of nitric acid in the final solution

The mass of nitric acid (HNO3) in the final solution can be calculated using the mass fraction of acid in the nitric acid solution.

Given: - Mass of nitric acid solution added = 100 g - Mass fraction of acid in the nitric acid solution = 6.3%

The mass of nitric acid (HNO3) can be calculated as follows:

Mass of nitric acid (HNO3) = Mass of nitric acid solution added * Mass fraction of acid Mass of nitric acid (HNO3) = 100 g * (6.3/100) Mass of nitric acid (HNO3) = 6.3 g

Step 4: Calculate the total mass of the final solution

The total mass of the final solution is the sum of the masses of water (H2O), sodium hydroxide (NaOH), and nitric acid (HNO3).

Total mass of the final solution = Mass of water + Mass of sodium hydroxide + Mass of nitric acid Total mass of the final solution = 0 g + 6.9 g + 6.3 g Total mass of the final solution = 13.2 g

Step 5: Calculate the mass percentages of each substance in the final solution

To calculate the mass percentages, we divide the mass of each substance by the total mass of the final solution and multiply by 100.

Mass percentage of water (H2O) = (Mass of water / Total mass of the final solution) * 100 Mass percentage of water (H2O) = (0 g / 13.2 g) * 100 Mass percentage of water (H2O) = 0%

Mass percentage of sodium hydroxide (NaOH) = (Mass of sodium hydroxide / Total mass of the final solution) * 100 Mass percentage of sodium hydroxide (NaOH) = (6.9 g / 13.2 g) * 100 Mass percentage of sodium hydroxide (NaOH) ≈ 52.27%

Mass percentage of nitric acid (HNO3) = (Mass of nitric acid / Total mass of the final solution) * 100 Mass percentage of nitric acid (HNO3) = (6.3 g / 13.2 g) * 100 Mass percentage of nitric acid (HNO3) ≈ 47.73%

Therefore, the mass percentages of all substances in the final solution are approximately: - Water (H2O): 0% - Sodium hydroxide (NaOH): 52.27% - Nitric acid (HNO3): 47.73%

Please note that these calculations are based on the given information and assumptions made about the reaction and the composition of the nitric acid solution.