Please help with formula and solutions: a) What is the molarity of a solution of
ID: 951814 • Letter: P
Question
Please help with formula and solutions:
a) What is the molarity of a solution of 25.0 mg of silver nitrate in 250 mL of water?
b) How many moles of potassium are preent in 100 mL of a 0.200 M of K2CrO7 solution?
c) What is the mass of the compound dissolved in 100 mL in 0.200 M of K2CrO7 solution?
d) What is the volume of a solution in which 0.294 moles of CH3COOH are present and the molarity is 20.0 mM?
e) How many mL need to be added to a 0.30 M solution if the initial volume is 20.0 mL and the desired final concentration is 0.0040 M?
f) What is the concentration of 43.0 mL of calcium hydroxide needed to neutralize 86.0 mL of perchloric acid with a concentration of 0.92 M?
g) What is the final volume of a 10 mL solution that initially had a concentration of 0.455 M and is diluted to a final concentration of 0.0055 M?
h) The reaction of 85.0 mL of a silver nitrate solution and 75.0 mL of a 0.9 M calcium chloride solution yields a precipitate with a mass of 7.96 g. Assuming that the concentration goes to completion (all the silver is precipitated), find the initial concentration of silver nitrate.
i) What is the concentration of 15.0 mL of potassium hydroxide needed to neutralize 10.0 mL of hydrochloric acid with a concentration of 0.8 M?
Explanation / Answer
a)
mass = 25 mg = 25*10^-3 of AgNO3
V = 250 ml = 0.25 L
change to mol
MW ag NO3 = 169.87
mol = mass/MW = (25*10^-3)/169.87 = 0.0001471
[AgNO3] = mol/V = 0.0001471/0.25 = 0.0005884 M
b)
mol of K in V = 100 = 0.1 L M = 0.2
K2CrO7 = 2 mol of K
mol = MV = 0.1*0.2*2 = 0.04 mol of K
c)
mol = MV = 0.1*0.2 = 0.02 mol of K2CrO7
MW = 242.1885
mass = mol*MW = 242.1885 *0.02 = 4.84377 g of K2CrO7
d)
n = 0.294 mol
M = 20*10^-3 M
V = mol/M = 0.294 /(20*10^-3) = 14.7 L
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