Chemistry Unit 2 Quiz KEY

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1 Form A (Master Copy) Chemistry Unit 2 Quiz KEY Standards: SC 1 a, 3 a, c, d DO NOT WRITE ON THIS TEST USE A SCRATCH SHEET OF PAPER! SAVE TREES, INCREASE SUTAINABILITY!!

2 Directions: Please choose the best answer choice for each of the following questions. 1. The chemical equation below shows the transformation of elements during the process of nuclear fusion. What is the mass and atomic number of Si in this chemical equation? A. B. C. D. To answer this question correctly you must be able to look at the periodic table and identify Si having an atomic number of 14. This means it has 14 protons; therefore, Si will always have an atomic number of 14 = subscript 14. Next you will notice in the products there is Si + y. y stands for gamma radiation. We know that gamma radiation does not have mass because it is electromagnetic radiation. Therefore all of the mass must be in Si. Add the two masses of Carbon 12 and Oxygen 16 = 28. Your answer should be C. Si atomic number 14 atomic mass In a nuclear reaction, and react under high temperature conditions to form. What is the atomic mass of nuclear reaction? A. 6 B. 10 C. 12 D. 20 formed during the To find the answer to this question you must work it exactly the same as question number one, but in this case it is only asking for the atomic mass of Ne in the products of the reaction. Oxygen 16 combined with Helium 4 will equal a combined mass of 20. The y stands for gamma, and gamma ray does not have any mass therefore the mass for Ne is If transuranium elements are not naturally occurring, which statement explains how they were discovered in the first place? Scientists used atomic filters to siphon off A. particles that were used to build the transuranium elements. Scientists used nuclear accelerators to fuse B. atomic nuclei together and form the transuranium elements. Scientists used cathode ray tubes to pile up C. electrons that fused and formed the transuranium elements. Scientists used special chemical reactions D. to blend neutrons and protons and form the transuranium elements. To find the best answer choice for this question you would need to dissect each answer choice to see which is more logical as solution to explaining how unnatural elements can be discovered. For answer choice A it is discussing atomic filters and siphoning particles. We have never discussed such a process in class, and if you think about how small an atom is would it be possible to filter them or siphon (suck/vacuum) of particles of an atom, NO. For answer B it is discussing using nuclear accelerator to fuse atomic nuclei together. We discussed in class how changing the number of protons via nuclear fusion completely changed the elements identity, and is how scientist theorized that all elements were made originally in stars. For answer choice C a cathode ray is associated with electrons. Your key here is that electrons cannot change an elements identity only form Ions of that element. For answer D changing nuclei of atoms is nuclear chemistry not chemical reactions. DataDirector Assessment ID: 429 Page 1 of 2011 Houghton Mifflin Harcourt. All rights reserved.

3 4. Laura is learning that the Sun, like other stars, shines because of the nuclear fusion reaction taking place in its center. Which process describes the nuclear fusion reaction taking place? A. A heavier nucleus splits to form lighter nuclei. B. Lighter nuclei join together to form a heavier nucleus. C. The heavier nuclei undergo collisions and emit energy. D. The lighter nuclei undergo collisions and absorb energy. The key term in the question here is fusion. Fusion contains the root fuse which means to combine. Add the logic of when you combine two things the product will be larger in some way and you will find that the correct choice is B lighter reactants to a heavier product.. Which of these statements about an electron is true? A. An electron is very small compared with an atom. B. An electron changes size depending on temperature. C. An electron is always located inside the nucleus of an atom. D. An electron stops moving if it does not receive energy from outside the atom. electrons and protons in an ion be described? A. balanced charge with fewer protons than electrons B. balanced charge with fewer electrons than protons C. unbalanced charge with more protons than electrons D. unbalanced charge with more electrons than protons To answer this question you need to have an understanding of how a neutral atom becomes an ion. An atom becomes an ion by changing the number of electrons creating an imbalance of charges. When there are equal numbers of protons and electrons the atom has a neutral charge. If you increase the number of electrons the atom becomes a negatively charged anion, if you decrease the number of electrons the atom becomes a positively charge cation. Therefore the correct answer choice for a negative ion (anion) of oxygen is D The correct answer is A, this is a fact questions that checks you knowledge of the most basic concept of the molecular theory/structure. 6. In relation to the atom, the nucleus has the A. most mass and least volume. B. most mass and most volume. C. least mass and most volume. D. least mass and least volume. This is also a fact based question; the answer is supported by Rutherford s Gold Foil experiments when he discovered that most of an atom is empty space. Therefore the atom is most dense or has the most mass in the nucleus. The nucleus like a penny on a football field is a very small portion of the overall volume. Therefore the correct answer is A. 7. An oxygen atom forms an ion. How can the charge and the relative numbers of DataDirector Assessment ID: 429 Page 2 of 2011 Houghton Mifflin Harcourt. All rights reserved.

4 8. The symbols below represent atoms and ions of the first four elements in the periodic table.,,, Which two particles have the same number of electrons? A. and B. and C. and D. and To answer this question, you use the same knowledge you used to answer question 7. The charges next to hydrogen and lithium represent they have a charge of positive 1, which means they have one less electron than they have protons. Hydrogen has 1 proton therefore to be a positive 1 cation it will have 0 electrons. Lithium has 3 protons; therefore, to have a charge of positive 1 it must have one less electron than protons; this means it will have 2 electrons. An atom of He has 2 protons, so to be neutral it will also have two electrons. Beryllium has 4 protons therefore it will also have 4 electrons in a neutral atom. The correct answer is B a positive 1 cation of Lithium (2 electrons 3 protons) has the same amount of electrons as a neutral atom of Helium (2 protons and 2 electrons). DataDirector Assessment ID: 429 Page 3 of 2011 Houghton Mifflin Harcourt. All rights reserved.

5 Directions: Review the content below and answer the questions that follow Fusion and fission reaction The equations below represent two nuclear reactions, where is a neutrino, is a gamma ray, is a positron, and is a neutron. The first equation represents the nuclear reaction in which hydrogen atoms combine to form helium. The Sun is powered by this reaction, which results in the release of large amounts of energy. The second equation represents the nuclear reaction of an unstable uranium atom. Many unstable heavy atoms undergo a nuclear reaction of this type, in one or more steps, until a final reaction produces stable nuclei. 9. Which term BEST describes the material represented by the symbol? A. compound B. isotope C. mixture D. molecule This question gives you a whole bunch of information that means absolutely nothing in regards to you answering the questions. Often on state test this will be the case from what I have experienced with my professional test taken and have come to understand about the test you will see in your future. This is not always the case but it will happen at some point. The question ask which term best describes the material represented by the symbol. If you look at the period iodic table you will see that the average atomic mass of Barium is approximately 137. This atom of Ba represented has a mass of 142. Barium atoms always have a proton number of 6 or it is not Barium, therefore they must have varying amounts of neutrons making the best answer choice B: Isotope. 10. Which of these symbols represents an isotope of an element? A. B. C. D. This questions test your knowledge of common symbols you could see in chemical equations/expressions for nuclear chemistry or nuclear decay. answer choice a would indicate an electron with a positive charge, which as of our current knowledge is not possible, Answer choice B would indicate a Hydrogen atom with 1 proton and 0 neutrons this is an Isotope of Hydrogen and is the correct answer; answer c represents a neutron, and answer D represent the anti-neutrino. DataDirector Assessment ID: 429 Page 4 of 2011 Houghton Mifflin Harcourt. All rights reserved.

6 Directions: Please choose the best answer choice for each of the following questions. 11. Which element has twelve protons in its nucleus? A. carbon B. chromium C. magnesium D. sodium Answer choice C is the correct answer. The Atomic number of Mg is 12, this means that Magnesium must always have 12 protons or it is not Magnesium. 12. The three isotopes of oxygen,,, and, have a relative abundance of,, and, respectively. Which statement BEST describes the atomic nucleus of oxygen? A. Oxygen atoms have 16 protons. B. Most oxygen atoms have 8 protons and 8 neutrons. C. Oxygen atoms can have differing numbers of protons. D. A small number of oxygen atoms has 9 protons and 9 neutrons. This question test your understanding of the average atomic masses of elements represented on the periodic table. Your knowledge of how to solve the weighted average atomic mass for elements should have helped you. If you remember I told you when you are solving for average atomic mass you could look at the atomic mass of the most abundant (highest percentage) isotope of the element and your average atomic mass should be closest to this number. The same concept exists here. The correct answer is B. All atoms of oxygen have 8 protons all the time every time, and Oxygen 16 is 99.76% abundant, this means that almost all Oxygen isotopes exist in this form. If all oxygen atoms have 8 protons and the mass of this isotope is 16 amu, then it must also have 8 neutrons. 13. Nitrogen, with atomic weight has two isotopes. One isotope weighs and has a relative abundance of 99.6%. The other one has a relative abundance of 0.37%. Compute the atomic weight of the less abundant isotope. A B..182 C D In order to solve this question you would need to work through the method of finding a weighted average atomic mass. First let s look at what we are given. We are given the following in the question. The average atomic weight of nitrogen is Nitrogen has 2 isotopes. Isotope 1 is 99.6% abundant and has an atomic mass of Isotope DataDirector Assessment ID: 429 Page of 2011 Houghton Mifflin Harcourt. All rights reserved.

7 2 is 0.37% abundant and it does not tell us the atomic mass of isotope 2 (I will write this unknown as mass 2 in the equation below) It asks use to compute the atomic weight of the less abundant isotope which I will do below. Notice that I go ahead and change the percentages to decimals before I put them into the equation. SET IT UP FIRST! amu = ( amu x 0.996) + ( Mass 2 x ) Now you must solve to get the variable Mass 2 on a side by itself. The first step is to go ahead and calculate or work what you can in this case the first parenthesis and it will give us the following. ( x 0.966) = amu amu = ( amu) + ( Mass 2 x ) Now move this to the opposite side by doing the opposite of the action it is involved with. It currently is attached to a + or addition sign so we must subtract ( ) from itself on the right and on the left amu = ( amu) + (Mass 2 x ) amu = - ( amu) + (Mass 2 x ) amu = (Mass 2 x ) Now we must remove from Mass 2. There is multiplication between these two therefore we must do the opposite which is divide amu = Mass 2 x amu = Mass 2 The best answer choice is D Short Answer: For the following questions do your best to answer each question prompt to the best of your ability. Use sig figs when applicable, always show your work, incorporate the correct units into your answer, and write in complete sentences. Be thorough in your explanations, and cover all aspects of the questions and prompts. All of these are worth points when applicable. 14. What is the symbol for an Alpha Particle? The Symbol is 4 2He What is the symbol for a Beta Particle? e What is the symbol for gamma radiation? Either the gamma letter y or a 17. Write the chemical equation expression of Beta nuclear decay for an atom of Iodine. In order to do this start with what you are given 128 3I In my equations the atomic numbers and the atomic masses will not be directly over/under each other as they should be in your writing. Next you know that beta decay will keep the mass of Iodine but one of the neutrons will turn to a proton increasing the atomic number from 3 to 4. The element that has 4 protons is Xenon so add Xe Now you should have 128 3I Xe + You should also know that Beta decay involves the release of an electron e- and an antineutrino v so add them in and you have your final answer I Xe + 0-1e v 18. Write the chemical equation expression of Alpha nuclear decay of an atom of Copper. Include gamma radiation in your expression. Work through this process in the same manner you did number 17. You know you are to start with DataDirector Assessment ID: 429 Page 6 of 2011 Houghton Mifflin Harcourt. All rights reserved.

8 Copper = 64 29Cu. This will be your reactant on the other side of the yield sign is your products. You know that an alpha particle is released which is a He atom with 2 protons and a mass of 4 amu. 4 2He. To find your other product subtract the atomic number of the Alpha particle from your initial element: 29 2 = 27, this will give you the element Cobalt, Co subtract the mass of the alpha particle to get your mass of the Co atom 64 4 = 60 now put it all together Cu He + 27Co 19. Define artificial and natural transmutation, differentiate between the two. Any time you are trying to discuss the difference between natural and artificial you will most always be right if you discuss natural as being a process that can happen in nature without Human manipulations. Artificial will always involve some type of human manipulation/interaction. 20. What does each variable/constant in the following equation stand for: E=mc 2 E = energy; m = Mass defect or mass deficit is acceptable; and c = the constant for the speed of light 21. Which elements tend to be more unstable, and why? In terms of reactivity groups such as 1 or 17 with a near empty or near full valence electron shell are the most reactive because they are so eager to become stable by having a full valence electron shell. In terms of nuclear stability, the larger atoms with larger nuclei are more unstable. The larger a nucleus gets the more protons it has and the more neutrons it needs to try and balance the repulsion of protons. The repulsion of the protons becomes greater and greater and the nuclear force or atomic force of an atomic that holds the nucleus together becomes more and more unstable or inferior. 22. Find the average atomic mass of the following isotopic mixture. 93.0% Molybdenum with an atomic mass of 48.3 amu, 6.200% Molybdenum with an atomic mass of amu, and % Molybdenum with an atomic mass of If you did not notice two of these Isotopes have the same atomic mass. This is a typo so let s solve it as if they were not the same. Average amu of Mo = (0.930 x 48.3) + ( x 48.30) + ( ) = = 48.3 amu (3 sig figs) 23. Explain how Rutherford s experiment helped to change the plum pudding model. Rutherford shot particles at gold foil and recorded what happened to the particles after they hit the foil. This proved that there was a nucleus to an atom, and that most of the atom was empty space. This is quite the opposite of the plum pudding model that has electrons and protons distributed evenly throughout the model. Rutherford s experiment was the first notion that there was something else in the nucleus besides a proton based on density. 24. Find the average atomic mass or Mg if 78.99% of Mg atoms have a mass of 23.9 amu, 10.00% have a mass of amu, the rest have a mass of Notice that there are only 2 percentages out of three. To find the third subtract the given two from 100%. 100% % % = 11.01% Average AMU Mg = ( x 23.9) + ( x ) + ( x ) = = 24.2 amu 3 significant figures. 2. If an atom of deuterium (H with an atomic mass of 2) and an atom of tritium (H with an atomic mass of 3) were to be bombarded against each other, what would this be called? Write a chemical expression to represent this. Explain the expression. This is Fusion DataDirector Assessment ID: 429 Page 7 of 2011 Houghton Mifflin Harcourt. All rights reserved. Go on to the next page»

9 . Chemistry Unit 2 Quiz» Form A (Master Copy) Explanation: Fusion describes a set of nuclear reaction in which two lighter nuclides, in this case deuterium and tritium, collide fusing nuclei. The product of this reaction is Helium, a free neutron, and ENERGY. Notice that the conservation of mass is supported from the reactants to the products. Chemical Equation: 2 1 H + 3 1H yield 4 2He n + ENERGY 26. If an atom of Uranium 23 were to undergo nuclear fission, this would occur in two steps. Write the first and second step of this phenomenon. Explain each individually in complete sentences. There are two steps to this. I will write the equation for the first step followed by an explanation of the first step. I will then write the equation for the second step followed by an explanation of the second step. Step 1: U n yields U Explanation of 1 st step: In the first step of the fusion of Uranium-23, Uranium-23 struck by a free neutron via nuclear fusion momentarily creating an atom of Uranium-236. Uranium is only in the stage for a very small fraction of a second before it splits in step two. Step 2: U yields 90 36Kr Ba n n n + ENERGY Explanation of 2 nd Step: Uranium will know technically undergo nuclear fission now that it is in its highly unstable form of Uranium-236. Uranium-236 can split into 1 of 0 different combinations of new atoms. 3 neutrons are produced in addition to the two new elemental products. A drastic amount of energy is released as a byproduct of nuclear reactions. The atomic numbers will always add up to equal the reactants atomic number, in this case 92. The atomic masses including those of the three neutrons will also add up together to equal the initial mass of the reactant Uranium-236 You could even go further to discuss calculating the amount of energy produced using Einstein s equation E=mc2 and mass defect or products vs reactant. DataDirector Assessment ID: 429 Page 8 of 2011 Houghton Mifflin Harcourt. All rights reserved.

Nuclear Physics and Nuclear Reactions

Slide 1 / 33 Nuclear Physics and Nuclear Reactions The Nucleus Slide 2 / 33 Proton: The charge on a proton is +1.6x10-19 C. The mass of a proton is 1.6726x10-27 kg. Neutron: The neutron is neutral. The