Multiple Choice
A 5.65 g sample of a weak acid with Ka=1.3×10⁻⁴ was combined with 5.20 mL of 5.90 M NaOH and the resulting solution was diluted to 750 mL. The measured pH of the solution was 4.20. What is the molar mass of the weak acid?
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2. Atoms & Elements
Calculating Molar Mass
Multiple Choice
What is the molar mass of chloroform (CHCl₃) given that a sample weighing 0.389 g is collected in a flask with a volume of 102 cm³ at 97°C and a pressure of 728 mmHg?
A
142.28 g/mol
B
98.96 g/mol
C
119.38 g/mol
D
153.82 g/mol
Verified step by step guidance1
Identify the chemical formula of chloroform, which is CHCl₃. This indicates that one molecule of chloroform consists of one carbon (C) atom, one hydrogen (H) atom, and three chlorine (Cl) atoms.
Determine the atomic masses of each element from the periodic table: Carbon (C) is approximately 12.01 g/mol, Hydrogen (H) is approximately 1.01 g/mol, and Chlorine (Cl) is approximately 35.45 g/mol.
Calculate the molar mass of chloroform by summing the atomic masses of all the atoms in the formula: Molar mass = (1 × 12.01 g/mol) + (1 × 1.01 g/mol) + (3 × 35.45 g/mol).
Perform the arithmetic to find the total molar mass of chloroform. This involves multiplying the atomic mass of each element by the number of atoms of that element in the molecule and then adding these values together.
Compare the calculated molar mass with the given options to identify the correct answer, which is 119.38 g/mol.
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