F04_E1A - Chemistry 111 Page 1 out of 5 Exam I / Fall 2004...

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

View Full Document Right Arrow Icon
Chemistry 111 Page 1 out of 5 Exam I / Fall 2004 Answer Key Show all your work in the space provided in order to receive any credit at all! 1. Which of the following is the formula for potassium permanganate? (02 pts) a) PMnO 2 . b) KMnO 2 . c) PMnO 4 . d) KMnO 4 . e) K 2 MnO 4 . 2. Name the following compound: SO 3 . Sulfur Trioxide . (02 pts) 3. A certain sample of carbon graphite has 3.21 × 10 22 carbon atoms. What is the mass of this sample? (06 pts) This is a simple conversion from atoms to moles to number of grams… 3.21#10 22 Catoms # 6.022 #10 23 Catoms 1molC # 1mol C 12.011g C = 0.640 g of C graphite. 4. How many oxygen atoms are there is a 22.22 g sample of Na 2 CO 3 (MW = 105.98)? (08 pts) This is similar to the previous question, but we are asking about number of O atoms, not sodium carbonate “molecules”. Therefore, 22.22 g Na 2 CO 3 # 105.98g Na 2 CO 3 1mol Na 2 CO 3 # 1molNa 2 CO 3 3 mol O # 1molO 6.022 #10 23 atoms = 3.789 × 10 23 O atoms . 5. An isotope of Calcium has a mass number of 45 and a charge of +2. This isotopic ion has 18 electrons, 20 protons, and 25 neutrons. (06 pts) Calcium is element #20, therefore it has 20 protons. Since the mass number is 45, then it must have (the difference) 25 neutrons. Finally, a charge of plus two tells us that it is missing two electrons. Therefore, it must have 18 electrons. 6. When the following operation is performed properly, we end up with 2 significant figures in the answer. (03 pts) 1111- 1020.000 222.222 #0.003210
Background image of page 1

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

View Full DocumentRight Arrow Icon
Chemistry 111 Page 2 out of 5 Exam I / Fall 2004 Answer Key Aha! We must solve the denominator first and the rules for subtraction are based on
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/08/2010 for the course CHEM 111 taught by Professor Kenney during the Spring '08 term at Case Western.

Page1 / 5

F04_E1A - Chemistry 111 Page 1 out of 5 Exam I / Fall 2004...

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

View Full Document Right Arrow Icon
Ask a homework question - tutors are online