University:
Purdue University
Course:
CHM 34201 | Inorganic Chemistry Laboratory
Academic year:

2021
Views:

96

Pages:

1
Author:

Leilani Contreras

Practice Questions Recitation #3 ANSWER KEY 1. Perform the following calculations, and report answers with correct significant figures and units. a. What is the molar mass of formic acid (CH2O2)? 46.03 g/mol b. Mass (in grams) of 0.773 mol CaH2? 32.5 g CaH2 c. What is the number of molecules in 0.0305 mol CH3OH? 1.84 x 1022 molecules of CH3OH d. What number of carbon atoms are in 0.585 mol C4H10? 1.41 x1024 C atoms 2. Consider a 3.40 g sample of ammonia (NH3) gas in answering the following questions: a. What is the molar mass of ammonia? Include units in your answer. 17.03 g/mol b. How many moles NH3 does this sample represent? 0.200 moles c. How many (actual number) NH3 molecules are there in this sample? 1.20 x 1023 molecules d. How many H atoms are there in this sample? 3.60 x1023 H atoms 3. Calculate the following quantities: a. What is the mass (in grams) of 0.0492 moles of carbon dioxide? 2.17 g CO2 b. Moles of magnesium nitrate in 5.35g of this substance? 0.0361 moles Mg(NO3)2 c. How many molecules are present in a 4.020 g sample of nitrogen dioxide? 5.262 x1022 molecules NO2 d. How many oxygen atoms are in 0.55 g of ammonium nitrate? 1.2 x1022 O atoms e. What is the mass (in grams) of 1.63 x 1021 silicon atoms? 0.0760 g Si 4. Determine the empirical formula for each of the following compounds if a sample contains: a. 0.0130 mol C, 0.0390 mol H and 0.0065 mol O Empirical = C2H6O b. 11.66 g iron and 5.01 g oxygen Empirical = Fe2O3 c. 40.0% C, 6.7% H and 53.3% O by mass Empirical = CH2O 5. What is the molecular formula for each of the following: a. Empirical formula CH2 and molar mass = 84 g/mol Molecular = C6H12 b. Empirical formula NH2Cl and molar mass = 51.5 g/mol Molecular = NH2Cl 6. Determine the empirical and molecular formula for each of the following: a. Styrene contains 92.3% C and 7.7% H by mass and has a molar mass of 104 g/mol. Empirical = CH Molecular = C8H8 b. Ibuprofen contains 75.69% C, 8.80% H and 15.51% O by mass, and has a molar mass of 206 g/mol Empirical and Molecular formulas both equal C13H18O2