Solutions to: Units and Calculations Homework Problem Set Chemistry 145, Chapter 1

Transcription

1 to: Units and Calculations Hoework Proble Set Cheistry 145, Chapter 1 Give the nae and abbreviation of the SI Unit for: a Length eter b Mass kilogra kg c Tie second s d Electric Current ap A e Teperature kelvin K Give the abbreviation and describe what the following units are used to easure: a eter length b liter L volue c cubic centieter c 3 volue d illiliter L volue e degree Celcius o C teperature f kelvin K teperature (absolute) 3 Give the nae and the abbreviation (without looking in the book) of the SI or etric prefix for: a 10-1 pico p b 10 6 ega M c 10-9 nano n d 10 - centi c e 10-3 illi f 10 9 giga G g 10 3 kilo k h 10-6 icro 4 Express the following nubers in scientific notation with the appropriate nuber of significant figures: a = 57 x 10 9 b 41410= 4151 x 10 4 c = 9416 x 10-4 d 7465 x 10 6 = 7465 x 10 8

2 Perfor the following calculations and give the answer in scientific notation with the correct nuber of significant figures (Note: The software used to perfor these calculations does not round significant figures The first answer given is the result of the calculation The second nuber is appropriately rounded) a = b = c = d = e = f = g = h = i = j = k 70 = l = Perfor the following atheatical operations and give the answer with the correct nuber of significant figures: a = b = c 5749 = d = (note: first add the nuerator to get 1634, but only has 3 SF)

3 7 Perfor the following unit conversions Express your answers in scientific notation with the appropriate nuber of significant figures (NOTE: the answers given below do not have the correct nuber of significant figures, but you should be able to deterine this by now Reeber that ost of these conversion factors are exact nubers, so the answer is liited by the nuber of significant figures as is given in the proble) a Convert 4901 inches into: feet, eters, centieters, illieters and kiloeters 490 in = ft ft = in ( 490 in) 1 ft 1 in = ft 490 in = = in ( 490 in) in = in = c in = c ( 490 in) 54 c 1 in = c 490 in = in = ( 490 in) 54 1 in = in = k k = = in ( k) ( 490 in) 10 3 k in 1 k in = in = k

4 b Convert 5480 feet into iles, kiloeters and eters 5480 ft = i i = ft ( 5480 ft) 1 i 580 ft = i 5480 ft = k k = ft ( 5480 ft) k ft = k 5480 ft = = ft ( 5480 ft) ft = c Convert 54 eters into kiloeters, centieters, illieters, icroeters, and nanoeters µ 10 6 = k k = ) 1 k 1000 = c c = ) 1 c 10 = k = c n 10 9 = = ) = = µ 1 µ = ) 1 µ 10 6 = µ = n n = ) 1 n 10 9 = n

5 d Convert 986 o F into o C and K Convert o F to o C: ( 986 3) 5 = Convert o C to K: = e Convert 65 iles per hour into: k per hour and s i = k k = i 65 i k i = k 65 i = i = sec 1 = sec 65 i i sec = 9051 sec 1 f Convert 315 into ft, in, and c = ft = ft 3808 ft = ft = in = in 3937 in = in = c = c 100 c = c

6 g Convert 50 c 3 into in 3, 3, L and L c 3 = in 3 in = c c 3 1 in 54 c 3 = in 3 c 3 = = c c c 3 = c 3 = liter liter = c 3 c 3 liter = liter 1000 c 3 c 3 = L L = c 3 c 3 L = L c 3

7 8 In the ovie Goldfinger, Jaes Bond foils a plot to break into Fort Knox 007 does soe quick ental calculations to deterine the feasibility of reoving the gold If the price of gold is $1400 per troy ounce (31035 gras), what is the ass (in kg) of 1 illion dollars of gold? What is the volue of 1 illion dollars of gold in L, L, and 3 dollar 1 First how uch does 1 illion dollars of gold weigh at $1400 per troy ounce troy_ounce 14 dollar 10 6 dollar 1 troy_ounce 14 dollar = troy_ounce troy_ounce g troy_ounce g 1 troy_ounce 1 kg 10 3 g = kg Note, this is: 10 3 kg = lb 10 3 kg = ton The volue of this gold ay be deterined fro the density of gold (193 g/c 3 ) You will have to look this up soewhere (Your textbook is a good place to start, another good reference is the CRC Handbook of Cheistry and Physics You should know where this is in the Library) density ass volue A few notes on Mathcad, the progra used to prepare these answers This will help you learn how to read these docuents density Ag 193 g c 3 ass Ag 10 3 kg volue Ag ass Ag density Ag volue Ag = L volue Ag = liter volue Ag = The equals sign The bold ( ) is for "sybolic" ath, it just shows an equation like a book would The equals with a colon (:=) is for "defining" a variable The regular equals (=) is for calculating a value Units Mathcad autoatically calculates units and displays answers using SI units, unless told otherwise I will soeties show each step in a unit conversion, but after the first chapter, you should be cofortable with this and I will just display the results Mathcad does not round Since properly rounding each answer is a lot of work, you are responsible for checking this

8 9 The following experient is perfored with an unknown liquid The liquid is added to a graduated cylinder with a ass of gras After 500 L of the liquid is added to the cylinder, the ass is gras Is the liquid water? How do you know? If it is not water, what could it be? Inforation given in the proble: ass cylinder g volue liquid 500 L ass total g Fro the total ass and the ass of the cylinder you can deterine the ass of the liquid: ass liquid ass total ass cylinder ass liquid = g Now that the ass of the liquid and the volue of the liquid are known, the density ay be deterined This is useful because the density of a copound is constant and ay be copared with tables of known values density ass volue density liquid ass liquid volue liquid density liquid = g L 1 The density of water at 5 o C, fro the CRC Handbook of Cheistry and Physics, is g/l Since this is very close to the density of the unknown liquid, the unknown COULD be water (It does not have to be since soe other liquid could have the sae density)

9 Now repeat the above calculations for the second unknown The experient is repeated with a second liquid, after 03 L of this liquid is added the ass of the cylinde gras Is the second liquid ethanol? How do you know? If it is not ethanol, what could it be? Inforation given in the proble: ass cylinder g volue liquid 03 L ass total g Fro the total ass and the ass of the cylinder you can deterine the ass of the liquid: ass liquid ass total ass cylinder ass liquid = g Now that the ass of the liquid and the volue of the liquid are known, the density ay be deterined This is useful because the density of a copound is constant and ay be copared with tables of known values density ass volue density liquid ass liquid volue liquid density liquid = g L 1 The density of ethanol at 0 o C, fro the CRC Handbook of Cheistry and Physics, is g/ L This is not consistant with the value calculated in this proble To find possible copounds, glance tough a table of densities and find soething with a density close to this experiental value This proble set and the solutions were prepared by: Scott Van Braer Departent of Cheistry Widener University Chester, PA svanbra@sciencewideneredu