{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Homework 2-solutions

# Homework 2-solutions - tran(pt4954 Homework 2 sutclie(51045...

This preview shows pages 1–2. Sign up to view the full content.

tran (pt4954) – Homework 2 – sutclife – (51045) 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices be±ore answering. NOTE: A²TER QUESTION 15 READ CARE²ULLY! Some questions will require you to consider the vant’Hof ±actor, i. I± the solute is stated to be a nonelectrolyte, or i± it is a sugar, i = 1. Assume complete dissocia- tion o± ionic compounds. 001 10.0 points The molar heat o± vaporization o± carbon disulFde (CS 2 ) is 28.4 kJ/mol at its nor- mal boiling point o± 46 C. How much energy (heat) is required to vaporize 1 g o± CS 2 at 46 C? Correct answer: 372 . 997 Joules. Explanation: 002 10.0 points How much heat energy is needed to raise the temperature o± a 52 g sample o± aluminum ±rom 29 . 3 C to 91 . 6 C? The speciFc heat o± aluminum is 0 . 897 J / g · K. Correct answer: 2905 . 92 J. Explanation: m = 52 g SH Al = 0 . 897 J / g · K Δ T = 91 . 6 C - 29 . 3 C = 62 . 3 C = 62 . 3 K q = ? SH Al = q m Δ T q = SH Al m Δ T = (0 . 897 J / g · K) (52 g) (62 . 3 K) = 2905 . 92 J 003 10.0 points Consider the ±ollowing speciFc heats SH H 2 O(s) = 2 . 09 J / g · C , SH H 2 O( ) = 4 . 18 J / g · C , and SH H 2 O(g) = 2 . 03 J / g · C. The heat o± ±usion ±or water is 334 J/g and the heat o± vaporization ±or water is 2260 J/g. Calculate the amount o± heat required to convert 65 g o± ice at - 35 C completely to steam at 131 C. Correct answer: 204 . 625 kJ. Explanation: SH H 2 O(s) = 2 . 09 J / g · C Δ H vap = 2260 J/g SH H 2 O( ) = 4 . 18 J / g · C Δ H fus = 334 J/g SH H 2 O(g) = 2 . 03 J / g · C m ice = 65 g T 1 = - 35 C T 2 = 131 C In this example, ice is converted to steam. ²ive separate steps take place here: 1) ice is warmed ±rom - 35 C to 0 C; 2) a phase change ±rom ice to water at 0 C; 3) water is warmed ±rom 0 C to 100 C; 4) a phase change ±rom water to gas at 100 C; 5) steam is warmed ±rom 100 C to 131 C. Each o± these steps involves a separate en- ergy calculation, and the sum o± the energies o± these Fve steps is the total amount o± heat required ±or the process. ²or processes that involve warming a solid, liquid, or gas, we use the equation q = (SH) mΔ T , where SH = speciFc heat, m = mass or moles, and Δ T = temperature change. ²or phase changes (solid to liquid or liquid to gas), we use q = Δ H vap or fus (m) , where again m = mass or moles. So ±or the Frst step, warming ice, we have q 1 = (65 g) p 2 . 09 J g · C P b 0 C - ( - 35 C) B = 4760 J . ²or the second step, the phase change ±rom ice to liquid: q 2 = (334 J / g)(65 g) = 21700 J .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 7

Homework 2-solutions - tran(pt4954 Homework 2 sutclie(51045...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online