Hi
sorry
i don’t know but maybe next time
Answer:
C. 30.0 g NaOH and add water until the final solution has a volume of 3.00 L.
Explanation:
Molarity of a substance , is the number of moles present in a liter of solution .
M = n / V
M = molarity
V = volume of solution in liter ,
n = moles of solute ,
from the question ,
M = 0.250M
V = 3.00 L
M = n / V
n = M * v
n = 0.250M * 3.00 L = 0.75 mol
Moles is denoted by given mass divided by the molecular mass ,
Hence ,
n = w / m
n = moles ,
w = given mass ,
m = molecular mass .
From the question ,
n = 0.75 mol NaOH
m = molecular mass of NaOH = 40 g/mol
n = w / m
w = n * m
w = 0.75 mol * 40 g/mol = 30.0 g
Hence , by using 30.0 g of NaOH and dissolving it to make up the volume to 3 L , a solution of 0.250 M can be prepared .
Answer:
The balloon is cooled at a constant pressure until the temperature is -11°C. What is the volume of the balloon at this stage?
Answer:
68.3%
Explanation:
First, let us look at the equation of reaction involving silver and magnesium chloride:
2Ag + MgCl2 ----> 2AgCl + Mg
1 mole of MgCl2 is required to precipitate 2 moles of Ag completely from the solution. That is a ratio of 1 to 2.
Now, mole of MgCl2 used to precipitate all the Ag
= molarity x volume
= 2.19 M x 2.89/1000
= 0.0063291 mole
Since 1 mole of MgCl2 would always require 2 moles of Ag, 0.0063291 mole will therefore require:
0.0063291 x 2 = 0.0126 mole of Ag
This means that 0.0126 mole of Ag is present in stephanie.
Mass of silver in stephanie = mole x molar mass
= 0.0126 x 107.8682
= 1.365 g
Thus, 1.365 g of silver is present in 2.00 g sample of stephanie.
Mass percent of silver in stephanie = 1.365/2.00 x 100
= 68.25% = 68.3% to the correct number of significant figure.
