Module 4 Answers

.pdf

School

University of the Sunshine Coast *

*We aren’t endorsed by this school

Course

105

Subject

Chemistry

Date

May 17, 2024

Type

pdf

Pages

Uploaded by DeanMandrillPerson1097 on coursehero.com

29/08/2023, 12:14 Module 4 Self Assessment Quiz: Introductory Chemistry Module 4 Self Assessment Quiz Due No due date Points 33 Questions 33 Time Limit None Allowed Attempts Unlimited Instructions The self assessment quiz covers the most important concepts for the whole module. Please make sure you complete the quiz and check the feedback to make sure that you understand why a particular answer is correct. Remember, self assessment quizzes are NOT counted for marks and you may do any self assessment quiz as many times as you like. BUT, both the mid-semester and final exams are based substantially on the self-assessment quizzes. Take the Quiz Again Attempt History Attempt Time Score LATEST Attempt 1 12 minutes 22 out of 33 Submitted Aug 29 at 12:13 Question 1 1/1 pts For most measurements, the three basic parts are: magnitude, units, dimensions. magnitude, precision, accuracy. magnitude, siginificands, exponents. Correctl magnitude, units, uncertainty. All measurements have a magnitude (how much). When magnitudes are written, inherent in the number is an indication about the amount of uncertainty.  Most measurements have units.  Note that rarely, some measurements have no units and are dimensionless.  For example, pH is dimensionless.  Having said that, most people love to use units even if they don't exist!  In the case of pH, we use the term "pH units" even though technically there is no such thing.  More on this in an upcoming module. Question 2 0/1pts 0.0020 written in scientific notation with the correct number of digits in the significand is: You Answered 200 x 1073 Correct Answer 20x 1073 2x 1073 2.0x 103 https://learn.usc.edu.au/courses/7725/quizzes/18464 1/13

29/08/2023, 12:14 Module 4 Self Assessment Quiz: Introductory Chemistry The tricky part is figuring out how many significant figures are in a number when it is written in decimal notation. If you know the number of significant figures in decimal notation, you can then write that same number in scientific notation, knowing that the number of digits in the significand is the number of significant figures. Now for this crazy decimal number, 0.0020 Any non-zero (in this case 2) is significant. Ask yourself what the zeros neighbouring the left and right of a decimal point are doing. The zero to the left of the decimal point is telling you that dot you see is a decimal point, not a flyspeck! The numbers to the right of decimal point is telling you how far away the first non-zero number is from the decimal point. In other words, these zeros are place keepers, giving you information about the location of the decimal point. The number 2 is clearly a measurement, so it is significant. What about the zero to the right of the 2? Ask yourself, does this zero give you any information about the location of the decimal point? No, it doesn't. This zero is not a placekeeper, but an actual measurement, and it is therefore significant. REMEMBER: The problem is that zero is used as both placekeeper and it also means zero, which means it can be a measurement. Okay, so this measurement has two significant figures. So, the number of digits in the significant is also - two. Question 3 1/1 pts 1x 10 L is equal to: 1 pL 1 GL Correct! 1nL 1mL 1 x 10° means 1 x # which means 0.000000001 a i Anyway, the number is a bit annoying. If you look at the Periodic Table, you will see a list of prefixes (magnitude), and you will see that the prefix "nano" can be used for 109 Question 4 0/1pts The molar mass of water is: 18 g 18 mole You Answered 18 g.mol Correct Answer 18 g.mol"! https://learn.usc.edu.au/courses/7725/quizzes/18464 2/13

29/08/2023, 12:14 Module 4 Self Assessment Quiz: Introductory Chemistry | Note the use of units and terminology here: molar mass g.mol™!, molecular mass amu. Question 5 1/1 pts 1.00 litre of water has a mass of 1000.0 g. How many moles of water are in one litre? Correctl 55.6 mol 1000.0 mol 18.0 mol 1.0 mol i We've just asked you how many moles of water are in a liter of water. What we are trying to illustrate with this question is how interchangeable mass and moles are (as long as you know the molar mass). The molar mass of water: The formula for water is H,O and the Periodic Table tells you the molar mass of hydrogen is 1.008 g.mol-! and oxygen is 15.999 g.mol-!. So, the molar mass of water is 2 x 1.008 g/mol +15.999 g/mol = 18.01 g/mol. Notice that we mixed up the /mol and mol! so you get used to using both. Okay, the mass of water in 1.00 L = 1000.0 g So the number of moles in 1.00 L : = | 1000.0 g moiar mass — = 55.6 mol 18.01 g.mol Question 6 1/1 pts 10°C expressed in Kelvin is: 273 K 263 K 10 K Correctl 283 K - To convert centigrade to Kelvin, you add 273. This figure, to 5 significant figures (273.15) is in your - Periodic Table. Question 7 1/1 pts 2.0 moles of water has a mass of: 18 g.mol 36 g.mol https://learn.usc.edu.au/courses/7725/quizzes/18464 3/13

29/08/2023, 12:14 Module 4 Self Assessment Quiz: Introductory Chemistry 18 g Correct! 36 g mass (g) = moles x molar mass (—%-) =2.0 moles x 18.0g.mol™ = 36g Question 8 0/1 pts How many moles of hydrogen atoms are in 24.3 g of water? You Answered 135 24.3 Correct Answer 270 18.0 nass - 243 g No. moles of water molecules = = — = 1.35 mol molar mass 18.0 g.mol ~ON | 36wt HO H-\H 1DO2. D 0:00/ 6:27 Question 9 1/1 pts The mass of 2.0 mol of carbon atoms is: 12 g/mol 129 24 mol Correct! 24 g https://learn.usc.edu.au/courses/7725/quizzes/18464 4/13

29/08/2023, 12:14 Module 4 Self Assessment Quiz: Introductory Chemistry mass (g) = moles x molar mass (#) =2.0 moles x 12.0g.mol™! = 24¢ Question 10 1/1 pts For the three measurements, 21.1 mL, 21.3 mL and 21.2 mL, you can likely say that: The measurements are neither accurate nor precise. The meaurements are both both accurate and precise. Correctl The measurements are precise, but you can NOT make a statement about accuracy. The measurements are accurate, but you can NOT make a statement about precision. Precision refers to how well a series of measurements agree to one another.  Accuracy refers to how well measurements agreed with published/accepted values. No information was given about this in the question and so no statement about accuracy can be made. Question 11 1/1 pts How many moles of water molecules are in 24.3 g of water? Correctl 135 18 0.74 24.3 nass - 243 g No. moles of water molecules = = — = 1.35 mol molar mass 18.0 g.mol Question 12 1/1 pts How many moles of oxygen atoms are in 24.3 g of water? 0.74 18 Correct! 135 24.3 https://learn.usc.edu.au/courses/7725/quizzes/18464 5/13

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version