57 58 When strongly heated, boric acid breaks down to boric oxide and water. Wha

Question

57 58

When strongly heated, boric acid breaks down to boric oxide and water. What mass of boric oxide is formed from the decomposition of 15.0 g B(OH)_3? 2 B(OH)_3 (s) rightarrow B_2 O_3 (s) + 3 H_2 O (g) a. 7.50 g b. 15.0 g c. 8.44 g d. 16.9 g e. 33.8 g The complete combustion of 0.26 moles of propone, C_3 H_8, will a. consume 0.26 mol O_2 and produce 0.26 mol CO_2. b. consume 0.26 mol O_2 and produce 0.52 mol CO_2. c. consume 1.3 mol O_2 and produce 0.78 mol CO_2. d. consume 1.3 mol O_2 and produce 3.9 mol CO_2. e. consume 1.3 mol O_2 and produce 1.0 mol CO_2. How many grams of dioxygen are required to completely burn 3.4 g of C_2 H_5 OH? a. 8.2 g b. 11 g c. 2.3 g d. 38 g e. 51 g If the complete combustion of an unknown mass of ethylene produces 16.0 g CO_2, what mass of ethylene is combusted? C_2 H_4 (g) + 3 O_2 (g) rightarrow 2 CO_2 (g) + 2 H_2 O(g) a. 0.182 g b. 0.364 g c. 5.10 g d. 8.00 g e. 12.6 g Calculate the number of moles of O_2 required to react with phosphorus to produce 2.82 g of P_4 O_6. (Molar 219.9 g/mol) a. 0.0128 mol b. 0.088 mol c. 0.0385 mol d. 0.0256 mol e. 0.077 mol

Explanation / Answer

(57) The balanced reaction is : C2H5OH + 3O2 -----> 2CO2 + 3H2O

Molar mass (g/mol) 46.1 32

From the balanced reaction,

1 mole = 46 g of C2H5OH reacts with 3 mol = 3x32 = 96 g of O2

3.4 g of C2H5OH reacts with M g of O2

M = ( 3.4x96) / 46

= 7.1 g of O2

(58) C2H4 + 3O2 ---> 2CO2 + 2H2O

Molar mass(g/mol) 28 44

From the above balanced reaction ,

2 mol = 2x44 g of CO2 produced from 1 mol = 28 g of C2H4

16.0 g of CO2 produced from N g of C2H4

N = ( 16.0x8)/(2x44)

= 1.45 g of C2H4

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