Final Examination for CHEM 101L, Fall 2017, Open Book with hints Student\'s Name

Question

Final Examination for CHEM 101L, Fall 2017, Open Book with hints Student's Name: Signature: If a solution contains 0.50 g SiO·025 g Naa, and 1.25 g NHCl, what is the mass percentage of NaCI in the mixture? Give your answer in two significant figures and show your work. 1. 2. A mixture containing Sio, NaCI, and NH,CI weighs 3.5 g. After subliming away the NH.CI from the mixture, the total weight of the mixture reduced to 2.7 g. What was the mass percentage of the NH,CI in the original mixture? 3. What is the name and chemical formula of the acid present in vinegar? 4. Calculate the weight of HCI in grams needed to make 500 mL of 2M solution of HCI. (Hint: Molar mass of HCl-36.46 g) 5. Write the structure of salicylic acid, methyl alcohol and methyl salicylate.

Explanation / Answer

Q1

mass of NaCl = 0.25 g

total mass = 0.50+0.25+1.25 = 2 g

NaCl % = mass of naCl / total mass * 100% = 0.25/2*100 = 12.5 % if NaCl

Q2

mass of NH4Cl in sample --> 3.5-2.7 = 0.8 g

% NH4cl = mass of NH4Cl / total mass * 100%

%NH4cl = 0.8/3.5*100 = 22.85%

Q3

name = acetic acid

formula CH3COOH

Q4

M = mol/V

M = 2, _V = 500 mL = 0.5 L

find mol

mol = MV = 2*0.5 = 1 mol of HC lrequired

mass = mol*MW = 1*36.46 g = 36.46 g

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