Module 2 Pretest Homework Packet  Answers

Module Two-Part H: Density, Specific Gravity & Volume Problems  5 points

1. A quartz rock was cut into a rectangular solid paperweight. IF the paperweight has a mass of 165 g and measures 5.00 cm by 5.00 cm by 25.0 mm, what is its volume in cubic centimeters?

### The Question:

____???____ cm3 = 5.00 cm X 5.00 cm X 25.0 mm

10 mm = 1 cm ; therefore 25.0 mm = 2.50 cm (all units must be equal)

Volune = L3 = 5.00 cm X 5.00 cm X 2.50 cm = ____62.5__cm3

2. Calculate the density in g/mL for 10.0 grams of ethyl ether having a volume 14.0 mL.

### The Question:

Density = ____???____ g/m

Density = Mass/Volume = 10.0 g/14.0 mL = 7.14 g/mL

Corwin 7th edition:

Page 60:  #43-#46; #47 - #58

Part I: Heat and Specific Heat                      5 points

1. Find the specific heat of gold if 25.0 cal is required to heat 30.0 g of gold from 27.7 oC to 54.9 oC.

Specific heat is the amount of heat required to raise the temperature of one gram of a substance one degree Celsius.

 Heat (cal) ( cal ) ---------------------------------------------------- = Specific Heat (C) -------- Mass (g) ∙ Temperature Change (∆t) g ∙ oC

q = C ∙ m ∙ ∆t

∆t = 54.9 oC – 27.7 oC = 27.2 oC

 25.0 cal ( cal ) ----------------------- = Specific Heat = 0.0306 -------- 30.0 g ∙  27.2 oC g ∙ oC

2. Calculate the heat required to raise to raise 25.0 g of iron (sp Heat=0.108 cal/g ∙ oC) from 25.0 oC to 50.0 oC.

q = C ∙ m ∙ ∆t

q =  (0.108 cal/g ∙ oC) (25.0 g) (50.0 oC – 25.0 oC )

q = 0.108 ∙ 25.0 ∙ 25.0 cal

q = 67.5 cal

Old Text References:

McMurry 6th 1032C text: Chapter 2 Section 2.10 see worked example 2.13 page 38, then try problems 2.20 and 2.21 page 39. End of Chapter page 46 Problems 2.64-2.71.

Corwin 5th CHM 1025C text Chapter 3 Section 3.9 see worked example 3.19 page 64; then try the practice exercise on page 64. Additional problems end of chapter page 69: #57-#64.

Corwin 7th See Section 11.6 pages 322-324. New text removes specific heat problems from Chapter 2.