Question

1)80г 10% раствора добавили 10г растворенного вещества. Какой стала массовая доля вещества в растворе 2)80г 10% раствора прилили 20 мл воды. Плотность волы 1 г/мл. Какой стала массовая доля вещества в растворе. 3) смешали 200г 10% и 200г 20% раствора соли. Найти массовую долю полученного вещества в растворе.

Answer 1

1) m 1 вещества = m 1 раствора * w 1 = 80 * 0,1 = 8 г
После того как добавили 10 г соли, m 2 вещества = 8 + 10 = 18 г, а m 2 раствора = 80 + 10 = 90 г
w 2 вещества = m 2 вещества / m 2 раствора = 18/90=0,2 = 20%

2. 1) m 1 вещества = m 1 раствора * w 1 = 80 * 0,1 = 8 г
m воды = плотность * V H2O = 1*20 = 20 г
m 2 раствора = 80 + 20 = 100 г
w 2 вещества = m вещества / m 2 раствора = 8/100= 0,08= 8%

3. m1 вещества = m1 раствора * w1=200*0,1= 20 г
m2вещества = m2 раствора * w2=200*0,2=40 г
m3 вещества = m1 вещества + m2 вещества = 20 + 40 = 60 г
m3 раствора = m1 раствора + m2 раствора = 200 + 200 = 400 г
w3 = m3 вещества/ m3 раствора = 60/400=0,15=15%

Answer 2

To solve these problems, we need to calculate the amount of the substance before and after the changes in the solutions. Let's go step by step:

1. Initially, we have 80g of a 10% solution. This means that 10% of the solution's mass is the dissolved substance (solute), and the rest is the solvent (probably water). To find the mass of the solute initially, we can use the following formula:

Initial mass of solute = 0.10 * Initial mass of the solution

Initial mass of solute = 0.10 * 80g = 8g

Now, 10g of additional solute is added to the solution. To find the final mass of the solute, we add the initial and additional masses:

Final mass of solute = Initial mass of solute + Additional mass of solute Final mass of solute = 8g + 10g = 18g

To find the final mass of the solution, we add the initial mass of the solution (80g) to the additional mass of the solute (10g):

Final mass of the solution = Initial mass of the solution + Additional mass of solute Final mass of the solution = 80g + 10g = 90g

Now, to find the final mass fraction (mass percentage) of the solute in the solution, we use the following formula:

Final mass fraction of solute = (Final mass of solute / Final mass of the solution) * 100%

Final mass fraction of solute = (18g / 90g) * 100% = 20%

So, the final mass fraction of the solute in the solution is 20%.

2. Initially, we have 80g of a 10% solution. This means that 10% of the solution's mass is the dissolved substance (solute), and the rest is the solvent (probably water). We will first find the mass of the solute and solvent in the initial solution.

Initial mass of solute = 0.10 * Initial mass of the solution Initial mass of solute = 0.10 * 80g = 8g

Initial mass of solvent = Initial mass of the solution - Initial mass of solute Initial mass of solvent = 80g - 8g = 72g

Now, 20ml of water is added to the solution. To find the mass of the added water, we use the density formula:

Mass of water = Volume of water * Density of water

Mass of water = 20ml * 1g/ml = 20g

Now, to find the final mass of the solution, we add the mass of the initial solvent and the added water:

Final mass of the solution = Initial mass of solvent + Mass of water Final mass of the solution = 72g + 20g = 92g

To find the final mass fraction (mass percentage) of the solute in the solution, we use the following formula:

Final mass fraction of solute = (Final mass of solute / Final mass of the solution) * 100%

Final mass fraction of solute = (8g / 92g) * 100% ≈ 8.7%

So, the final mass fraction of the solute in the solution is approximately 8.7%.

3. We have two solutions to mix: 200g of 10% solution and 200g of 20% solution. We will first find the mass of the solute and solvent in each initial solution.

a) For the 200g of 10% solution: Initial mass of solute (10% solution) = 0.10 * 200g = 20g Initial mass of solvent (10% solution) = 200g - 20g = 180g

b) For the 200g of 20% solution: Initial mass of solute (20% solution) = 0.20 * 200g = 40g Initial mass of solvent (20% solution) = 200g - 40g = 160g

Now, let's find the total mass of the solute and solvent after mixing:

Total mass of solute = Mass of solute (10% solution) + Mass of solute (20% solution) Total mass of solute = 20g + 40g = 60g

Total mass of solvent = Mass of solvent (10% solution) + Mass of solvent (20% solution) Total mass of solvent = 180g + 160g = 340g

To find the mass fraction (mass percentage) of the solute in the final solution, we use the following formula:

Mass fraction of solute = (Total mass of solute / Total mass of the solution) * 100%

Total mass of the solution = Total mass of solute + Total mass of solvent Total mass of the solution = 60g + 340g = 400g

Mass fraction of solute = (60g / 400g) * 100% = 15%

So, the mass fraction of the solute in the final solution is 15%.