Question

1. A system does 425 kJ of work and loses 125 kJ of heat to the surroundings. What is the change in internal enery of the system? a) 550 kJ c) -300 kJ e) OkJ b) 300 kJ d) - 550 kJ 2. How many grams of NaBr (102.89 g/mol) are contained in 250.0 mL of a 0.200 M solution of sodium bromide a) 50.0 g c) 5.14 g c) 0.0500 g b) 20.6 g d) 0.486 g 3. A sample of gas occupies a volume of 600 mL. As the expands, it does 202 J of work on its surroundings at a constant pressure of 1.25 atm. What is the final volume of the gas in ml? e) 162200 ml a) 162 mL b) 1600 mL c) 2200 ml d) 161600 ml. 4. What is the molar concentration of a solution that results from diluting 25.0 mL of a 0.45 M solution of KOH 500.0 mL? a) 44 M b) 11 M c) 9.0 M d) 0.11M e) 0.022 M 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 c) 496 kJ e) 13660 kJ b) 262 kJ d) 6830 kJ 6. How many grams of Nal (149.89 g/mol) are required to produce 92.2 g of Pb12 (461.00 g/mol)? Pb(NO3)2(aq) + 2Nal(ag) Pb12() + 2NaNO3(aq) a) 567 g c) 60.0 g e) 92.9 g b) 284 g d) 30.0 g

Answer 1

1)

W = -425 KJ

Negative because system is doing work

Q = -125 KJ

Negative because system is losing heat

Use:

Delta E = Q + W

= -125 KJ - 425 KJ

= -550 KJ

Answer: d

2)

volume , V = 2.5*10^2 mL

= 0.25 L

use:

number of mol,

n = Molarity * Volume

= 0.2*0.25

= 5*10^-2 mol

use:

mass,

m = number of mol * molar mass

= 5*10^-2*1.029*10^2

= 5.14 g

Answer: c

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