Question

5. How much heat is produced by the combustion of 5.25 g of acetylene (C2H2, 26.036 g/mol)? 2C2H2+502( 4CO2(@+ 2H20( AH -2602 kJ a) 131 kJ b) 262 kJ c) 496 kJ d) 6830 k e) 13660 kJ 10 6. How many grams of Nal (149.89 g/mol) are required to produce 92.2 g of Pbl2 (461.00 g/mol)? Pb(NO 3)2(aq) + 2NaI (a) Pbl2)+ 2NANO3(ag) a) 567 g b) 284 g c) 60.0 g d) 30.0 g e) 92.9 g

Answer 1

5)

Molar mass of C2H2,

MM = 2*MM(C) + 2*MM(H)

= 2*12.01 + 2*1.008

= 26.036 g/mol

mass(C2H2)= 5.25 g

use:

number of mol of C2H2,

n = mass of C2H2/molar mass of C2H2

=(5.25 g)/(26.04 g/mol)

= 0.2016 mol

Since Δ H is negative, heat is released

when 2 mol of C2H2 reacts, heat released = 2602.0 KJ

So,

for 0.2016 mol of C2H2, heat released = 0.2016*2602.0/2 KJ

= 262 KJ

Answer: b

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