17. How many moles of ammonia, NHs, are in 13.81 g of NHs? A) 1.234 moles B) 0.8

Question

17. How many moles of ammonia, NHs, are in 13.81 g of NHs? A) 1.234 moles B) 0.8124 moles C) 8.316x 104 moles D) 4.881 x 103 moles E) 235.3 moles 18. How many molecules are in 555.4 g of benzene, C&Ho;? A) 1.18×10-23 molecules B) 4.29 x 104 molecules C) 8.46x 102 molecules D) 4.70 x 104 molecules E) 3.34x 1026 molecules 19. What is the mass percent of carbon in CaH&0? A) 13% B) 24% C) 35% D) 46% E) 52% 20. What is the coefficient of H:0 when the following equation is properly balanced with the smallest set of whole numbers? Na + HzO NaOH + H2 A) 1 B)2 C)3 D)4 E) 5

Explanation / Answer

17. I mole NH3 contains = avagadro numbe of NH3 molecules or moles.

mole of NH3 = ( weight/Mol.weight) = 13.81/17 = 0.812 moles

0.812 moles contains = 0.812 x 6.023 x 1023 moles of NH3

= 4.88 x 1023 moles

Answer is D. 4.88 x 1023 moles

18. 1 g benzene contains avagadro number of molecules.

555.4 g contains how many molecules ?

555.4 x 6.023 x 1023 = 3.34 x 1026 molecules.

Answer is E

19. Mass percent = (2 x carbon/ Total molecular weight) x 100 = (2 x 12/46) x 100 = 52 %

ANswer is E.

20. 2 Na + 2 H2O ....> 2NaOH + H2

Answer is B) 2

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