A is obviously out because it leads to a volume of 125.0 milliliters of the new solution and gives you a lower concentration than you were aiming for.
D is out because you are adding 75 milliliters of the stock solution, so your concentration would be too high. You only need 25.0 milometers of stock solution per 100 milliliters of the new solution.
C is also out because it leads to 50.0 milliliters stock solution per 100 milliliters of the new solution and hence the wrong concentration.
B is by default the correct answer. It also details the correct technique. First you add the stock solution (This you know from your calculations to be 25 milliliters.) then you add the water up to the volume you needed. (Because the calculations only tell you the total volume of water not what you need to add) You also add the water last so you can rinse the neck of the flask to make sure you also get all the stock solution residue into the stock solution.
I would add the final step of stirring, but B is the only answer that can be correct.
Answer:
Mass = 99.8 g
Explanation:
Given data:
Mass of potassium nitride = ?
Mass of nitrogen produced = 10.65 g
Solution:
Chemical equation:
2K₃N→ 6K + N₂
Moles of nitrogen:
Number of moles = mass/ molar mass
Number of moles = 10.65 g / 28 g/mol
Number of moles = 0.38 mol
Now we will compare the moles of nitrogen with potassium nitride.
N₂ ; K₃N
1 : 2
0.38 : 2×0.38 =0.76
Mass of potassium nitride:
Mass = molar mass × number of moles
Mass = 131.3 g/mol × 0.76 mol
Mass = 99.8 g
Answer:
a) To determine the facilities that contribute the most to recycling check the pie chart and select the facility with the largest portion while to determine the facilities that contribute the least to recycling check the pie chart and select the facility with the smallest portion
b) Energy is saved because the products which are recycled usually require less energy to turn them into usable materials
c) It saves energy through recycling. It helps sustains the environment. It decrease the emission of green house gases
Explanation:
The question is not complete
a) Pie chart is the graphical representation of information in which the information is represented in a circle. The circle is divided into segments and the portion with the largest segment has the highest percentage.
To determine the facilities that contribute the most to recycling check the pie chart and select the facility with the largest portion while to determine the facilities that contribute the least to recycling check the pie chart and select the facility with the smallest portion
b) Extraction and processing of raw resources to make end products requires a lot of energy. With recycling energy is saved because the products which are recycled usually require less energy to turn them into usable materials
c) It saves energy through recycling. It helps sustains the environment. It decrease the emission of green house gases.
C or A I may be incorrect but those are what I think it is
Answer:
pH = 9.48
Explanation:
We have first to realize that NH₃ is a weak base:
NH₃ + H₂O ⇔ NH₄⁺ + OH⁻ Kb = 1.8 x 10⁻⁵
and we are adding this weak base to a solution of NH₄NO₃ which being a salt dissociates 100 % in water.
Effectively what we have here is a buffer of a weak base and its conjugate acid. Therefore, we need the Henderson-Hasselbach formula for weak bases given by:
pOH = pKb + log ( [ conjugate acid ] / [ weak base ]
mol NH₃ = 0.139 L x 0.39 M = 0.054 mol
mol NH₄⁺ = 0.169 L x 0.19 M = 0.032 mol
Now we have all the information required to calculate the pOH ( Note that we dont have to calculate the concentrations since in the formula they are a ratio and the volume will cancel out)
pOH = -log(1.8 x 10⁻⁵) + log ( 0.032/0.054) = 4.52
pOH + pH = 14 ⇒ pH = 14 - 4.52 = 9.48
The solution is basic which agrees with NH₃ being a weak base.
