CHEM 101 Worksheet, Chapter 3: Mass Relationships in Chemical Reactions Multiple
ID: 1028730 • Letter: C
Question
CHEM 101 Worksheet, Chapter 3: Mass Relationships in Chemical Reactions Multiple choice questions: circle the correct answer(A-E) Show your work questions (p. 2): show all work! Use the amu for each element from the periodic table! Navo = 6.02x 1023 1. Atom X has two isotopes: 25.03t% is 3"X and 75.0% is 3 . what is the average molar mass of X? A. 36.0 amu 2. The molar mass (in amu) of ZnS04.6HQ A.161.5 3. How many atoms of Na in 5.10 moles of Na2CO? A.3.07x1023 4. What is the mass in grams of 1.00x101 atoms of lead, Pb? A.3.44x10-10g 5. 0.2 mol NasCO3 gn,4.24 g NasCOs moles A. 530g. 449 molB21.2g, 449 mol C. 530g, 0.051 mol D. 21.2g, 0.040 mol E. 16.6g, 0.051 mol 6. The % composition in tin(IV)oxide A, 21 %Sn, 79%0 B. 88%Sn, l 2%O C. 12%Sn, 88%() D. 94%Sn, 6%O E. 79%Sn 21%O 7. A compound has the following Wt% composition: 2.1% H, 65.3% 0,32.6% s, what is its empirical formula? A. H:SO4 D. 35.5 amu D. 53.5 1.84x1025 D. 3.44x10g E. 34.5 amu E. 215.5 E. 10.2 B. 72.0 amu C. 36.5 amu C. 269.5 C. 6.14x1023 C. 1.25x1038 g B. 179.5 B. 6.14x104 B. 2.07x10114 g E. 125x1014g % Sn %O (Sn = tin, element # 50 ) B. H4S.OR C. S4HO D. H2SO2 E. HO4S How many gram Na in 5.00g Na2SO? A. 0.035 g 9. A compound containing only carbon and hydrogen has 85.7xt% C and 14.3 Wtgab. Its molar mass is 56 amu. What is its molecular formula? A. C4H 10. Balance the following reactions. No fractional cogfficients coefficients must be the lowest whole B. 1.31 g C. 1.62 g D. 0.97 E. 0.81 B. C-H4 C. C2H D. CH2 E. CH a) K+ H2O H:O + c) C.Hs 02 H3PO4 H20 11. How many g of Co are formed from the combustion of 2.9 g of butane, C4Ha with excess oxvgen? The balanced reaction is: 2CaH10+ 10Oz 8CO2 + 10H2O A. 0.26g 12. How many g 12 will react with 20.4 AL to form Alb (aluminum iodide)? As always, first balance the reaction! (Hint: this is nota limiting reagent problem) A. 144 13. For the balanced reaction: Nt(g) 3H2(g) 2NH1(g). How many moles of NH3 will be produced when 0.50 mol N2 reacts with 1.0 mol H2? B. 6.6g C. 8.8g D. 10.5 E. 2.2g B. 288. G C. 192. G D. 72 g E. 576 g B. 1.0 mol C. 0.50 mo E. 3.0 mol 14. Calculate the mass of C02 formed when 2.3 g of ethanol, C2HsOH reacts with 3.2 g oxygen O2 to form CO2 and H20. (You balanced the reaction in 8.e)! This is a limiting reagent problem! A. 4.6 B. 2.2g D. 6.6g E. 2.93gExplanation / Answer
1. OPTION D. Average atomic mass of an element is given as f1M1 + f2M2 +… + fnMn where f is the fraction of the natural abundance of the isotope and M is the mass number of the isotope. The fractions of each isotope is the number of each isotope in natural abundance for every 100 atoms of that element. From the percentage of abundance, fraction can be calculated by dividing the percentage abundance by 100.
Thus, the average atomic mass of X is (0.25*37) + (0.75*35) = 35.5amu.