Question

How many grams of oxygen are formed when 6.21 moles of KOH are formed? 4 KO(s) + 2 H_2O(l) rightarrow 4 KOH(s) + O_2(g) 19.9g 27.9g 49.7g 3.59g 11.7g Consider the following balanced reaction. How many grams of water are required to from 75.9g of HNO_3? Assume that there is excess NO_2 present. Molar masses: H_2O = 18.02g. HNO_3 = 63.02g. 3 NO_2(g) + H_2O(l) rightarrow 2 HNO_3(aq) + NO(g) 38.0g 21.7g 43.4g 10.9g 26.5g A 12.39g sample of phosphorus reacts with 42.54g of chlorine to from only phosphorus trichloride (PCl_3). If it is the only product what mass of PCl_3 is formed? 30.15g 54.93g 140.01g 79.71g 91.86g Determine the theoretical yield of HCl if 60.0g of BCl_3 and 37.5g of H_2O are reacted according to the following balanced reaction. Molar mass is BCl_3 = 117.16g/mol BCl_3(g) + 3 H_2O(l) rightarrow H_3BO_3(s) + 3 HCl(g) 75.9g HCl 132g HCl 187g HCl 56.0g HCl 25.3g HCl Give the percent yield when 28.16g of CO_2 are formed from the reaction of 4.000 moles of C_8 H_18 with 4.000 moles of O_2. 2 C_8H_18 + 25 O_2 rightarrow 16 CO_2 + 18 H_2O 20.00% 25.00% 50.00% 21.50% 37.50% Automotive air bags inflate when sodium azide decomposes explosively to its constituent 2N_a N_3 (s) rightarrow 2N_a (s) + 3N_2 (g) How many grams of sodium azide are required produce 33.0g of nitrogen? 1.77 0.785 76.6 51.1 114.9 If the percent yield for the following reaction is 65.0%, how many grams of KClO_3 are needed to produce 32.0g of O_2? 2 KClO_3(s) rightarrow 2 KCl(s) + 3 O_2(g) 53.1g 81.7g 126g 283g 88.1g Calcium oxide reacts with water in a combination reaction to produce calcium hydroxide: CaO (s) + H_2O (l) rightarrow Ca(OH)_2 (s) A 4.50-g sample of CaO is reacted with 4.34g of H_2O How many grams of water remain after the reaction is complete? 0.00 0.00892 2.90 1.04 0.161 Sodium metal and water react to from hydrogen and sodium hydrogen. If 5.98g of sodium react with water to form 0.26g of hydrogen and 10.40g of sodium hydroxide, what mass of water was involved in the reaction? 4.68g 5.98g 10.14g 10.66g 6.65g

Answer 1

1) The balanced reaction is 4KO(s) + 2H2O(l) ---> 4KOH(s) + O2(g)

From the balanced reaction ,

4 moles of KOH formed along with 1 mole =32 g of O2

6.21 moles of KOH formed along with ( 6.21 mol * 32g) / 4 mole = 49.7 g of O2

2) The balanced reaction is 3NO2(g) + H2O(l) ---> 2HNO3(aq) + NO(g)

From the balanced reaction ,

2 moles = 2*63.02g = 126.04 g of HNO3 produced from 1 mole = 18.02 g of water

75.9 g of HNO3 produced from (75.9g*18.02g)/126.04g = 10.9 g of water

3)The balanced reaction is 2P+3Cl2--> 2PCl3

Molar mass(g/mole)          31     71        137.5

2 moles = 2*31=62 g of P reacts with 3 mole = 3*71=213 g of Cl2

12.39 g of P reacts with (12.39*213)/62 = 42.54 g of Cl2

So both reactants all completely reacted

So 2 mole = 2*31=62 g of P produces 2 mole = 2*137.5 g of PCl3

12.39 g of P produces (12.39*2*137.5)/62 = 54.93 g of PCl3

(4) The balanced reaction is BCl3 + 3H2O ---> H3BO3 + 3HCl

Molar mass ( g/mole)          117          18                         36.5

1 mole = 117 g of BCl3 reacts with 3 moles = 3*18 = 54 g of H2O

60.0 g of BCl3 reacts with (60.0g*54g)/117g = 27.7 g of water

So (37.5 - 27.7)g of water left unreacted and is the excess reactant

Since all the mass of BCl3 reacted completely BCl3 is the limiting reactant

From the balanced reaction ,

1 mole = 117 g of BCl3 produces 3 moles = 3*36.5g of HCl

60.0 g of BCl3 produces ( 60.0g*3*36.5g) / 117g = 56.0 g of HCl