Use the References to access important values if needed for this question. The f

Question

Use the References to access important values if needed for this question. The following information is given for magnesium at 1 atm: Boiling point-1090.0°C Melting point-649.0°C Specific heat solid= 0.2431 cal/g°C Specific heat liquid = 0.3200 cal/g°C Heat of vaporization= 1.296 × 103 cal/g Heat of fusion 88.03 cal/g A 48.80 g sample of solid magnesium is initially at 631.0°C. How many kcal of heat are needed to raise the temperature of the sample to 768.0°C? kcal Submit Answer Retry Entire Group 4 more group attempts remaining

Explanation / Answer

Heat needed to raise the temperature from 631 C to 649 C

Q1 = m x Cps x (T2-T1)

= 48.80 g x 0.2431 cal/gC x (649 - 631)C

= 213.539 cal

Phase change at 649 C from solid to liquid

Q2 = m x Hf

= 48.80 g x 88.03 cal/g

= 4295.864 cal

Heat needed to raise the temperature from 649 C to 768 C

Q3 = m x Cps x (T2-T1)

= 48.80 g x 0.32 cal/gC x (768 - 649)C

= 1858.304 cal

Total heat needed = 213.539 + 4295.864 + 1858.304

= 6367.707 cal

= 6.367 kcal

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