Chapter07

# Chapter07 - Solutions for Chapter 7 End-of-Chapter Problems...

This preview shows pages 1–3. Sign up to view the full content.

ACS Chemistry Chapter 7 suggested solutions 1 Solutions for Chapter 7 End-of-Chapter Problems Problem 7.1. (a) Assuming all the food energy, 180 Cal, from eating a slice of pizza goes to keep your heart beating at 1 J of energy for each beat, the number of beats that can be sustained is: 180 Cal = (180 Cal) 1 kcal 1 Cal 4184 kJ 1 kcal 1000 J 1 kJ 1 beat 1 J = 7.5 × 10 8 beats At a pulse rate (heartbeat rate) of about 80 per minute, this would keep you going for about: 7.5 × 10 8 beats = (7.5 × 10 8 beats) 1 min 80 beats = 9.4 × 10 6 min [ 5 yr] (b) If the efficiency of use of this food energy is about 27%, the value calculated for capturing the energy from glucose oxidation in Section 7.9, the answers in part (a) would be only 27% as large: 2.0 × 10 8 beats; 2.5 × 10 6 min [ 18 yr] Problem 7.2. (a) Once they have been ignited both the pasta and potato chip, in Investigate This 7.1, continue to burn on their own. They release energy in the form of light and enough thermal energy to keep their temperatures high enough to continue burning. You might find that a potato chip burns somewhat better than pasta, because the fat is a better fuel than starch. This is reflected in their nutritional Calorie values as well. A gram of starch provides about 4 Calories (17 kJ) and a gram of fat about 9 Calories (38 kJ). (b) The oxidation of glucose is used as an example throughout this chapter. You know that the oxidation is quite exothermic, which is shown by the burning pasta, potato chip, and marshmallow (mainly sugars including glucose). It doesn’t matter that the glucose units are strung together as a polymer in starch or separated in a marshmallow -- each still oxidizes to produce a large output of enthalpy. Problem 7.3. If a baked, rather than a fried, potato chip were used in Investigate This 7.1, the baked chip will still burn, but probably not to burn as vigorously as the fried chip because there is less residual fat available as fuel on the baked chip. The raw potato slice may not burn at all because it has a high water content. The Olestra® chip will also burn quite well, for the Olestra is a long-chain polymeric fatty acid. It does not produce heat value in the body because it cannot be metabolized. Problem 7.4. Potential energy and kinetic energy are the two types of energy. Mechanical energy and thermal energy are both examples of kinetic energy. [Chemical energy stored in chemical bonds is a form of potential energy not included in this listing.] This is a visual representation of the relationship.

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

View Full Document
Chemical Energetics: Enthalpy Chapter 7 2 ACS Chemistry Chapter 7 suggested solutions energy kinetic energy potential energy mechanical energy thermal energy Problem 7.5.
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 02/23/2012 for the course CHEM AP taught by Professor Hx during the Fall '11 term at Manitoba.

### Page1 / 36

Chapter07 - Solutions for Chapter 7 End-of-Chapter Problems...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online