1) A 75 cm3 block of iron is removed from an 800Cfurnace and immediately dropped
ID: 1430860 • Letter: 1
Question
1) A 75 cm3 block of iron is removed from an 800Cfurnace and immediately dropped into 200 mL of 20C water. What percentage of the water boils away?
2) A rigid cylinder contains 9.0 g of nitrogen at 20 C. What is the minimum amount of heat energy that must be removed to liquify the nitrogen? Express your answer with the appropriate units.
3) A 9.0 g ice cube at -20 C is in a rigid, sealed container from which all the air has been evacuated. The specific heat at constant volume of steam is 1500 J/kgK. How much heat is required to change this ice cube into steam at 230 C ? Express your answer to two significant figures and include the appropriate units.
Explanation / Answer
1. Energy released by iron block to come from 800C to 100C = mCDT = (density of iron)(Volume of iron)(heat capacity of iron)(temperature difference) = 7850*75*10^-6*450*700 = 2472.75 J
Energy required for x p.c. water to reach 100 degrees = mCdT = x%*0.2* 4179*80 = 668.64 x
energy required for x pc of waer to evaporate = mL = 2257*10^3*0.2*x% = 4514x
4514x + 668.64x = 2472.75 = 0.477 p.c. of water
2. Energy required to liquify nitrogen = mCdt + mL = 0.009*[20.8*[20-(-210)]/0.014 + 25700] = 3306.72 J
3. Energy required to change this into steam = mCdt + mL(fusion) + mCDT + mL(vap) + mCDT = 0.009(2030*20 + 33400 + 4179*100 + 2264760 + 1500*130) = 26.364036 kJ
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