12. Write the appropriate nuclear symbol for each of thefollowing isotopes: (a) Z = 11, A = 23 (b) Z = 28, A = 64 (c) Z =50, A = 115 (d) Z = 20, A = 42
20. Ethane and acetylene are two gaseous hydrocarbons. Chemicalanalysis show that one sample of ethane contains 2.65 g of carbonand 0.668 g of hydrogen, and one sample of acetylene contains 4.56g of carbon and 0.382 g of hydrogen. Write reasonable empiricalformulas for these compounds. Ethane: Acetylene:
22. The atomic masses of 35Cl (75.53%) and 37Cl (24.47%) are34.968 amu and 36.956 amu, respectively. Calculate the averageatomic mass of chlorine. The percentages in parentheses denote therelative abundances ________ amu 26. Consider the combustion ofcarbon monoxide (CO) in oxygen gas: 2CO(g) + O2(g) → 2CO2(g)Starting with 3.09 moles of CO, calculate the number of moles ofCO2 produced if there is enough oxygen gas to react with all theCO
27. The fertilizer ammonium sulfate, (NH4)2SO4, is prepared bythe reaction between ammonia (NH3) and sulfuric acid 2NH3(g) +H2SO4(aq) → (NH4)2SO4(aq) How many kilograms of NH3 are needed toproduce 3.60 × 105 kg of (NH4)2SO4? Enter your answer in scientificnotation.
28. Identify each of the following as a combination,decomposition, or combustion reaction: C2H4O2(l) + 2O2 → 2CO2(g) +2H2(l) 2Na(s) + Cl2(g) → 2NaCl(s) 2NaH(s) → 2Na(s) + H2(g)
35. (a) What is the Na+ concentration in each of the followingsolutions: 3.05 M sodium sulfate: M 1.98 M sodium carbonate: M0.185 M sodium bicarbonate: M (b) What is the concentration of alithium carbonate solution that is 0.795 M in Li+? 37.A sample of0.7960 g of an unknown compound containing barium ions (Ba2+) isdissolved in water and treated with an excess of Na2SO4. If themass of the BaSO4 precipitate formed is 0.8916 g, what is thepercent by mass of Ba in the original unknown compound?
