Question

7. Consider a 100.0 grams of ammonium sulfide (10 points). (a) Write the Chemical formula of ammonium sulfide: emical formula of ammonium sulfide: NH4t (b) What is the molar mass of ammonium sulfide: (C) Find the moles of the compound (formula units present in 100.0 grams of ammonium sulfide: (d) Find the moles of ammonium ions present in 100.0 grams of ammonium sulfide: (e) Find the moles of hydrogen atoms present in 100.0 grams of ammonium sulfide: 8. Broader Application-Inquiry about Gold (10 points) There is a 10.0 grams necklace made of 18K gold. K, karat, is a measurement of the fineness (or purity) of Rold by Jeweler and gold dealers. Compared with 24K (pure gold), 18K means that the mass percent of gold is R = 0.75 (or 75 wt%, we treat it as an exact number here). In another word, that necklace contains 75% gold by mass. If the international gold price today is $1323 (US) per troy ounce, and one troy ounce equals 31.103 grams, solve the following two questions: (a) How many gold atoms are contained in this necklace? (b) Neglecting the price/cost of the other metals (25 wt%, usually silver and other metals by mass) present in the 18K gold, find the value/price of this necklace according to its gold content. (c) Since density of gold is higher than that of other metals, do you think the volume percent of gold in this piece is higher, or equal, or lower than 75 v% (volume percent)?

Answer 1

consider 100 gms of Ammonium sulfide. chemical formula - since The Ammonium cation NH4 has a lt charge, and the Sulfide anion sa has a 2- charge it follows that the chemical formula of Ammonium sulfide will look like g (NH4S. modar mass of (NH 4 ) 25 molt I Atomic masses : H = 1:008 mmol sa 32.07 gm.mol N = 14.01 gm. mol | => ON = 2 x 14.01 = 28.02 8 H = 8 x 100 = 8.064 Is = I x 32.07 = 32.07 68.15 gm/mode I Find The moles of the compound Formula units) present in 100 gms of Amonium sulphide. 7 100 gram 7 mole (NH4). S - 68:15_go =1.46735 moles of (NH4)2S

3 if one mode contain of (NH4)2 contain 6.022 X 1023 formula units you get that, 1.46735 modes X 6.022 xloes form units 1 more = 8.83 63 x 1023 form units → Find the moles in loogm of in this formula . cation contain of H-atoms prent Ammonium sulfide Hals I Amonium 4 h atom : no. of H atoms = ax 4 -28 Finally, if one formula unit 8 atoms of H you will get → contain 2.8.83 xlook's form units X 8 atoms of H - 1 form units = 70.64 x lots atoma oft = 7.0 64 X1094 atoms of HI

Find the modes of NHLt ion present in 100 gms of ammonium sulfide ? mass of NHI = 18 gm /mol i but (NH,25 in a 2 NH T ion present sog : 4 x NH" = 2 x 1 8 = 3 6 99 - Nhation :. 36gm what present 68.15 gm/male (NHS Them Z 1 00gm (NHOS . gms of what ion= 100 x 36 68.15 T=52,82 9m NHA Ion وہی modes of WHAT = mass of NH4tion mod. wt of what ion - 58.82 68.15 am am 163 moles | What ion present in 100 gms (NHutaso