Because it's protected from air because air makes it turn brown.
Complete Question:
A chemist adds 55.0 mL of a 1.1M barium acetate (Ba(C2H3O2)2) solution to a reaction flask. Calculate the mass in grams of barium acetate the chemist has added to the flask. Round your answer to 2 significant digits.
Answer:
15 g
Explanation:
The concentration of the barium acetate is given in mol/L (M), thus, the number of moles (n) of it is the concentrantion multiplied by the volume (55.0 mL = 0.055 L):
n = 1.1 * 0.055
n = 0.0605 mol
The molar mass of the substance can be calculated by the sum of the molar mass of each element, which can be found at the periodic table. Thus:
Ba = 137.33 g/mol
C = 12.00 g/mol
H = 1.00 g/mol
O = 16.00 g/mol
Ba(C2H3O2)2 = 137.33 + 4*12 + 6*1 + 4*16 = 255.33 g/mol
The molar mass is the mass divided by the number of moles, thus the mass (m) is the molar mass multiplied by the number of moles.
m = 255.33 * 0.0605
m = 15.45 g
Rounded by 2 significant digits, m = 15 g.
