AP Chemistry Bloom High School

1. A sample of C 3 H 8 O that contains 200 molecules contains _____ C atoms. (200 molecules)(3 atoms/molecule)= 600 C atoms

2. When the following equation is balanced, the coefficient of C 3 H 8 O is _____. C 3 H 8 O (g) + O 2(g)  CO 2(g) + H 2 O (g) Organics are harder to balance, especially of things split up, like the O’s! Try starting with C or H 2C 3 H 8 O (g) + O 2(g)  3CO 2(g) + 8H 2 O (g)

3. How many grams of H are in 46g of CH 4 O? 5.8g H

4. S and O react in a combination reaction to produce SO 3, an environmental pollutant. In a particular experiment, the reaction of 1.0g S with 1.0g O 2 produced 0.80g SO 3. The % yield in this experiment is _____. 2S (s) + 3O 2(g)  2SO 3(g) 1. Find Theoretical Yield and Limiting Reagent (1.0g O 2 )/( g O 2 /mol O 2 )=0.0312mol O 2 used (1.0g S)/(32.065g S/mol S)=0.0312mol S used Because the number of moles is the same, there is no limiting reagent Theoretical yield = 1.0g + 1.0g = 2.0g Experimental yield = 0.80g %yield = (Experimental yield)/(Theoretical Yield) x 100% (0.80/2.0)(100) = 40%

5. Al and O 2 react in a combination reaction to produce Al 2 O 3. The maximum amount of Al 2 O 3 that can be produced from 2.5g Al and 2.5g O 2 is _____. 4Al (s) + 3O 2(g)  2Al 2 O 3(s) (2.5g Al)/( g Al/mol Al)=0.0927mol Al (LR) (2.5g O 2 )(mol O 2 / g O 2 )(2mol O/1mol O 2 )=0.1563mol O

6. When the following equation is balanced, the coefficient of H 2 O is _____. Ca (s) + H 2 O (l)  Ca(OH) 2(aq) + H 2(g) Ca is already balanced. Count O and H on each side. Twice as many on product side as reactant side. Ca (s) + 2H 2 O (l)  Ca(OH) 2(aq) + H 2(g)

7. Al and O 2 react in a combination reaction to produce Al 2 O 3. In a particular experiment, the reaction of 2.5g Al and 2.5g O 2 produced 3.5g Al 2 O 3. The %yield of the reaction is _____. Theoretical Yield (from #5) = 4.7g Al 2 O 3 Experimental Yield = 3.5g Al 2 O 3 %yield = (Experimental yield)/(Theoretical Yield) x 100% (3.5/4.7)(100) = 74%

8. Fe(CO) 5 reacts with PF 3 and H 2, releasing CO. The reaction of 5.0mol Fe(CO) 5, 8.0mol PF 3 and 6.0mol H 2 will release _____mol CO. Fe(CO)5 + PF3 + H2  Fe(CO)2(PF3)2H2 + CO 5.0mol Fe(CO)5 is the limiting reagent (least moles) Balance first! Start with Fe to see if the complex is okay Fe(CO)5 + 2PF3 + H2  Fe(CO)2(PF3)2H2 + 3CO (5.0mol Fe(CO)5)(3mol CO/1mol Fe(CO)5)= 15mol CO

9. S and F 2 react in a combination reaction to produce SF 6. In a particular experiment, the percent yield is 79.0%. This means that in this experiment, a 7.90g sample of F 2 yields _____g SF 6. S (s) + 3F 2(g)  SF 6(g) (7.90g F 2 )(1mol F 2 / g F2)(1mol SF 6 /3mol F 2 )( g SF 6 /1 mol SF 6 ) = 10.12g SF 6 (10.12g SF 6 )(79.0%) = 7.99g SF 6

10. What is the empirical formula of the compound that contains 27.0% S, 13.4% O, and 59.4% Cl by mass? (27.0g S)(1mol S/32.065g S)= 0.842mol S (13.4g O)(1mol O/ g O)= 0.838mol O (59.4g Cl)(1mol Cl/35.453g Cl)= 1.68mol Cl {0.842, 0.838, 1.68}/0.838 = {1.00, 1.00, 2.00} S 1 O 1 Cl 2  SOCl 2

11. When the following equation is balanced, the coefficients are _____. NH 3(g) + O 2(g)  NO 2(g) + H 2 O (g) This problem involves trial and error, mostly because the O splits into two places. 4NH 3(g) + 7O 2(g)  4NO 2(g) + 6H 2 O (g)

12. AgNO 3 and AlCl 3 react with each other by exchanging anions. What mass of AgCl is produced when 4.22g of AgNO 3 react with 7.73g of AgCl 3 ? 3AgNO 3(aq) + AlCl 3(aq)  Al(NO 3 ) 3(aq) + 3AgCl (s) (4.22g AgNO 3 )/( g AgNO 3 /mol AgNO 3 ) =0.0248mol AgNO 3 (LR) (7.73g AlCl 3 )/(133.34g AlCl 3 /mol AlCl 3 ) =0.0580mol AlCl 3

13. What is the maximum amount of SO 3 that can be produced by the reaction of 1.0g S with 1.0g O 2 ? S (s) + O 2(g)  SO 3(g) Balance first! 2S(s) + 3O 2 (g)  2SO 3 (g) (1.0g S)/(32.065g S/mol S)=0.0312mol S (LR) (1.0g O2)(mol O 2 / g O 2 )(2mol O/1mol O 2 ) =0.0625mol O

14. When the following equation is balanced, the coefficient of Al 2 O 3 is _____. Al 2 O 3(s) + C (s) + Cl 2(g)  AlCl 3(s) + CO (g) Start with Al Al 2 O 3(s) + C (s) + Cl 2(g)  2AlCl 3(s) + CO (g) Then Cl Al 2 O 3(s) + C (s) + 3Cl 2(g)  2AlCl 3(s) + CO (g) Then O Al 2 O 3(s) + C (s) + 3Cl 2(g)  2AlCl 3(s) + 3CO (g) Then C Al 2 O 3(s) + 3C (s) + 3Cl 2(g)  2AlCl 3(s) + 3CO (g)

15. When the following equation is balanced, the coefficient of H 2 O is _____. K (s) + H 2 O (l)  KOH (aq) + H 2(g) When H 2 O and OH groups are involved, it’s easier to think of H 2 O as HOH K (s) + HOH (l)  KOH (aq) + H 2(g) Start with H K (s) + 2HOH (l)  KOH (aq) + H 2 Then OH K (s) + 2HOH (l)  2KOH (aq) + H 2 Then K 2K (s) + 2HOH (l)  2KOH (aq) + H 2

16. When the following equation is balanced, the coefficient of HCl is _____. CaCO 3(s) + HCl (aq)  CaCl 2(aq) + CO 2(g) + H 2 O (l) Ca (ok), C (ok), O (ok) Double H and Cl on reactant side only! CaCO 3(s) + 2HCl (aq)  CaCl 2(aq) + CO 2(g) + H 2 O (l)

17. When the following equation is balanced, the coefficients are _____. Al(NO 3 ) 3 + Na 2 S  Al 2 S 3 + NaNO 3 Start with Al 2Al(NO 3 ) 3 + Na 2 S  Al 2 S 3 + NaNO 3 Then NO 3 2Al(NO 3 ) 3 + Na 2 S  Al 2 S 3 + 6NaNO 3 Then Na 2Al(NO 3 ) 3 + 3Na 2 S  Al 2 S 3 + 6NaNO 3 S is already good! 2Al(NO 3 ) 3 + 3Na 2 S  Al 2 S 3 + 6NaNO 3

18. A compound is composed of only C, H, O. The combustion of a 0.519g sample yields 1.24g CO 2 and 0.255g H 2 O. What is the empirical formula of the compound? (1.24g CO 2 )(1mol CO 2 / g CO 2 )=0.0282mol CO 2 (0.255g H 2 O)(1mol H 2 O/18.015g H 2 O)=0.0142mol H 2 O mol C mol O mol H C H O C 1 H 1 O 3 (reduced)

19. Predict the product in the combination reaction below. Al(s) + N2(g)  _____ Al forms Al +3 N forms N -3 AlN

20. When the following equation is balanced, the coefficient of HNO 3 is _____. HNO 3(aq) + CaCO 3(s)  Ca(NO 3 ) 2(aq) + CO 2(g) + H 2 O (l) Start with H 2HNO 3(aq) + CaCO 3(s)  Ca(NO 3 ) 2(aq) + CO 2(g) + H 2 O (l) Then NO3 (ok), then Ca (ok), then C (ok)… 2HNO 3(aq) + CaCO 3(s)  Ca(NO 3 ) 2(aq) + CO 2(g) + H 2 O (l)

21. What is the coefficient of O 2 when the following equation is completed and balanced? C 4 H 8 O 2 + O 2  ___ + ___ It is a combustion reaction, therefore: C 4 H 8 O 2 + O 2  CO 2 + H 2 O Start with C C 4 H 8 O 2 + O 2  4CO 2 + H 2 O Then H C 4 H 8 O 2 + O 2  4CO 2 + 4H 2 O Then O C 4 H 8 O 2 + 5O 2  4CO 2 + 4H 2 O

22. Write the balanced equation for the reaction that occurs when CH 3 OH is burned in air. What is CH 3 OH’s coefficient? Any burning in air is a combustion reaction CH 3 OH + O 2  CO 2 + H 2 O Some organic equations are very tricky. Start with a low number for the first coefficient and balance from there. 2CH 3 OH + O 2  CO 2 + H 2 O Start with C 2CH 3 OH + O 2  2CO 2 + H 2 O Then H 2CH 3 OH + O 2  2CO 2 + 4H 2 O Then O 2CH 3 OH + 3O 2  2CO 2 + 4H 2 O

23. Mg and N 2 react in a combination reaction to produce Mg 3 N 2. In a particular experiment, a 9.27g sample of N 2 reacts completely. The mass of Mg consumed is _____. 3Mg + N 2  Mg 3 N 2

24. When the following equation is balanced, the coefficient of H 2 O is _____. N 2 O 5(g) + H 2 O (l)  HNO 3(aq) Start with N N 2 O 5(g) + H 2 O (l)  2HNO 3(aq) Then O (ok) Then H (ok) N 2 O 5(g) + H 2 O (l)  2HNO 3(aq)

25. S and F react in a combination reaction to produce SF 6. The maximum amount of SF 6 that can be produced from the reaction of 3.5g of S and 4.5g of F 2 is _____. S (s) + 3F 2(g)  SF 6(g) (3.5g S)/(32.065g S/mol S)=0.1092mol S (4.5g F 2 )(1mol F 2 /38.00g F 2 ) =0.1184mol F 2 (0.1184mol F 2 )(1mol SF 6 /3mol F 2 )( g SF 6 /1mol SF 6 ) = 5.77g SF 6

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