CHEM 120 Week 3 Exam 1 (Information)

CHEM120 Students: The first exam in your science course is approaching. The General Education Academic Support is here to help. What can you do ahead of Exam 1? 1. Attend a live exam review Thursday, May 12th 6 PM MT Exam 1 Review Join Meeting here: Click here to join 2. Watch the recording of an exam review Click here to watch recorded exam review 3. Schedule a 1:1 appointment with a tutor Click here to book 4. Review the topic videos from weeks 1 and 2 Click her to review Take a look at the review guide: Here is some information about Exam 1. Covers content learned in weeks 1 and 2. Is worth of 100 total points, and includes the following types of questions: o Multiple-choice questions o Multiple response questions o Matching questions o Essay questions Week 1 Topics: Scientific method Hypothesis: A testable explanation. Independent variable: What you as the scientist are controlling or changing. Dependent variable: Depends on the independent variable. What you expect to change. What you are measuring. Positive control: Group or condition with known outcome. Negative control: Condition for which no change is expected. Experimental controls: All the conditions that are held constant. Sample question: Q1. You have observed that your heart rate increases upon exercise, having caffeine and when you are scared. You want to conduct a study and of these which one is easily controllable independent variable? 1. Exercise 2. Amount of caffeine 3. Mental status 4. Heart rate Ans 1. Q2. You want to test two pain killer drugs A and B for their effectiveness in treating headaches. Based on the literature available and the chemical composition of the drugs you think drug A is more effective than B. You would like to determine which one is the most effective. State your hypothesis, design an experiment, and state a result that would support your hypothesis. Remember to include positive and negative controls. What is the independent and dependent variable of this experiment? Name the constant variables of this experiment. (8 points) Ans Hypothesis: Drug A is more effective than drug B in treating headaches. Experimental design: will have 4 groups of 6 patients of the same age, and gender, with headaches. Group 1 will receive Tylenol with water (known to treat headaches and serves as positive control), Group 2 will receive drug A with water (test group 1), Group 3 will receive drug B with water (test group 2) and Group 4 will receive just a sugar pill and water(negative control). After giving the drugs, measure the number of hr it takes to get complete relief from the headache. Results: The result shows, that the number of hrs to get complete relief from the headache is less in the case of drug A than drug B then our hypothesis is supported. Independent variable: drugs tested Dependent variable: duration of the headache Constant variable: age, sex, health conditions, drugs, caffeine intake. Q 3. I am studying the effect of exercise on heart rate. Which will be the independent variable of this experiment. a. Heart rate b. Hours of exercise c. Hours spent on measuring the heart rate d. Hours of rest Ans b. Dimensional Analysis DA Tips • Always, ALWAYS, write your units • Memorize the conversions (Powerpoint and Edapt) o Imperial to metric (Gal to L, tsp to ml, etc) o Metric prefixes (1000 mx = 1 x, 100 cx = 1x) • Always set up your start and end point before using conversions Examples: 1. I have a book with a weight of 0.46 lbs. What is the mass of this book in kg? Answer: 0.46 lbs 1 kg 0.21 kg 2.2 lbs 2. I have a sample of a fluid with a volume of 670 ml. What is the volume of this sample in gal? Answer: 670 ml 1 L 1 gal 0.18 gal 1000 mL 3.785 L 3. I have a sample that diffused to a diameter of 0.2 inches. What is this diameter in mm? Answer: 0.2 inch 2.54 cm 1 m 1000 mm 5.08 mm 1 inch 100 cm 1 m Do not forget about density! Formulas : D = M/V M = D x V V = M/D Where D = Density, M =Mass and V= volume Q1. In an experiment, you calculate that the mass of a 95.5 ml sample of a liquid is 75 grams. You know that this liquid is one of the substances below: Which liquid do you have? Liquid Density Liquid W 0.75 g/ml LIquid X 0.785 g/ml Liquid Y 0.35 g/ml Liquid Z 6.50 g/ml Density = Mass/Volume = 75grams/95.5 ml = 0.785 g/ml (Always remember to write the units, there is some point for the correct unit) Q 2: If a silver nugget occupies a volume of 8 ml what will be the mass of this metal? (density of silver is 10.5 g/ml). V = 8 ml M =? D = 10.5 g/ml Formula: Density (D) = mass (M) / volume(V) So, M = D x V D x V = 10.5g/ml x 8ml = 84 g (please remember to use the correct unit to earn 1 pt) Atoms What do we know about atoms? • Atoms are the smallest unit of an element that remain that element • Made of protons, neutrons, and electrons • They can combine to form molecules • An atom’s identity is determined by the atomic number (number of protons) • Atoms of elements are represented by chemical symbols (Al, U, Mg, etc.) • Different atoms of a given element can exist as Isotopes. These are atoms of the same element that differ based on their mass number Subatomic particles and their relationships • Protons, +1 charge, 1 AMU mass • Neutron, 0 charge, 1 AMU mass • Electron, -1 charge, ~0 AMU mass • Atomic number is the number of protons • An atom on the periodic table has the same number of electrons as it does protons by default • Neutrons + Protons = Mass Number • Atomic number is an average of the masses of atoms of an element, taking abundance of each isotope into account Applications: 1. I have an isotope with an atomic number of 48 and a mass number of 130. How many protons, electrons, and neutrons would I expect this atom to have, and what is this element? Answer: 48 protons because of atomic number(# of protons) of 48 48 electrons as we are assuming this is not an ion and therefore, we expect the protons and electrons to balance out. Since mass number is p + n = A, then n= A-p = 130 – 48 p = 82 neutrons Element is Cd based on the 48 atomic number (DO NOT Identify based on atomic mass) 2. I have an isotope of Oxygen with 9 neutrons. What is the mass number of this isotope? Answer: I know oxygen must have 8 protons because protons determine the element. So: p + n = A = 8 p + 9 n = 17 So, the mass number of this isotope is 17 3. What is the mass number of a Ti isotope with 46 neutrons? A. 68 B. 46 C. 22 D. 80 Ans A. The atomic number of Ti is obtained from the periodic table and then add the number of neutrons to get the mass number since the mass number is p + n = A Ions What do we know about ions? • Charged particle (atom or molecule) • Ions arise from an imbalance of protons and electrons due to the loss or gain of electrons • Cations have a positive charge • Anions have an negative charge • Ions form to have a more stable, Nobel gas like configuration (8 valance electrons) • They form to be like the nearest Nobel gas • Are great electrical conductors Applications: 1. What would be the charge of an ion of oxygen? Answer: O is in the 6th column of the periodic table, so we will expect it to gain a -2 charges as an ion. We could also know this as it will follow the octet rule: O has 6 valance electrons and will gain two more electrons (each with a -1 charge) to get to 8 valance electrons. This will give us a -2 charge. This will make oxygen have a similar electron configuration to Neon, the nearest Nobel gas on the periodic table. 2. What would be the electron configuration of an Mg ion? Answer: Mg normally has an electron configuration of 1s2 2s2 2p6 3s2. As an ion, Mg, being a metal, will lose two electrons, giving the resulting Mg ion, a +2 charge. Since we removed to electrons, this change must be reflected in the electron configuration: Mg2+: 1s2 2s2 2p6 will be the electron configuration as we took away the two electrons in the 3s2 orbital. 3. Determine which ion has the ground-state electron configuration of: 1s22s22p6 1. F- 2. Br 3. F 4. I Ans 1. 4. How many valance electrons (outermost electrons) will each of the following have? a. Na Answer: 1 b. H Answer: 1 c. Be2+ Answer: 2 valance electrons as this is like He, nearest Nobel gas d. N3- Answer: N starts with 5 valance electrons, the -3 means we have 3 additional electrons, so we have a total of 8 valance electrons e. S Answer: 6 f. I- Answer: I starts with 7 valance electrons, the -1 means we have 1 additional electron, so we have a total of (7+ 1) = 8 valance electrons 5. An ion has 12 neutrons, 11 protons, and 10 electrons. What is the charge of this ion? A. +1 B. +2 C. -1 D. +2 Ans A. The charge is the number of protons – the number of electrons that is 11-10 = +1 6. Use your understanding of ions and ground-state atoms to determine how many electrons you would expect each of the following species to contain: A. Copper (II) ion B. Chloride C. Oxygen D. Sodium-ion Ans Copper (II) ion = 27 Chloride = 18 Oxygen = 8 Sodium ion = 10 Compounds: Ionic: Ionic compounds contain a metal cation and nonmetal monoatomic anion or polyatomic anions. Be familiar with the naming, and writing the molecular formula of ionic compounds Named based on metal ion and nonmetal ion that ends with “ide” Application 1. Select all the substances that have ionic bonds A. MgCl2 Magnesium chloride B. H2O C. NaOH Sodium hydroxide D. NaCl Sodium chloride E. Ca3N2 Calcium nitride F. Mg (NO3)2 Magnesium Nitrate G. CO2 H. SO3 Ans A, C, D, E, and F 2. What is the molecular formula of Calcium sulfate = CaSO4 Sodium chloride NaCl Iron (III) sulfide: Fe2S3 Copper (III) Phosphate Cu3(PO4)2 Magnesium Nitrate Mg (NO3)2 3. An atom of Al reacts with an atom of Sulfur. Al 3 + and S 2- ions are formed and the two atoms form an ionic compound: Al2S3. In this reaction, the Sulfur atom: a. Gains electrons b. Losses electrons c. Gains protons d. Gains neutrons Ans: a Molecular Compounds or Covalent Compounds Molecular or covalent compounds contain two or more nonmetal ions and are named by using prefixes such as di, tri, tetra, etc. try to name the following. H2S, NO2, CO2, CO, P2S5, Cl2O5, N2S3, NH4 + Sample questions: 1. The name of the compound Cl2O5 is a. Chlorine pentoxide b. Dichlorine pentoxide c. Dichlorine tetroxide d. Chlorine pentoxide Ans b. 2. The bond between two oxygen atoms would best be described as a(n) a. Ionic bond b. Single covalent bond c. Double covalent bond d. Triple covalent bond Ans: c Polarity: These terms are only, ONLY, used for covalent bonds. NOT IONIC Polar: Unequal sharing Nonpolar: Equal sharing Polarity examples. Identify each of the following as containing polar or non-polar bonds: • N2O4 polar • S8 nonpolar • SBr2 polar • O3 nonpolar • O2 nonpolar • PF3 polar 1. Which of the below contains a polar bond? Select all that apply. a. N2 b. NBr3 c. O4F3 d. MgBr2 e. Na2O Answer: only b and c. d and e are both IONIC bonds, and a is a nonpolar bond. 2. What are hydrogen bonds? Ans : Hydrogen bonds are formed because of sharing of hydrogen between two other more electronegative atoms!! Application 1. Which of the following species would you expect to form intermolecular hydrogen bonds? A. O2 B. NaCl C. HBr D. Na+ Ans C, the compound should have hydrogen to form the hydrogen bonds!! For example, H2O molecules form hydrogen bonds with other water molecules. Because of that, they have a high boiling point and thus are liquid at room temperature. So, if a sample is liquid at temperature means its molecules may be held by intermolecular hydrogen bonding compared to another sample which is gas at the same temperature. Lewis dot structure Dots represent valance electrons We have 4 orbitals, each able to hold two dots (valance electrons) We want to add only one electron to each orbital until we run out of orbitals, then we can pair. This is because electrons repel. Examples: Lewis dot structure for carbon: Lewis dot structure for Iodine: Lewis dot structure for Oxygen: Lewis dot structure for Phosphide: Phosphide would have a 3- charge: P3- so: Lewis dot structure of H2O: Ionization energy: Refers to the energy need to remove an electron from an atom of a given element. As we move from the lower left to the upper right, ionization energy increases. Determine which of the following would have the greater ionization energy: • Fr and Br Br • O and Pb O • F and P F Electron configuration: This tells us where the electrons in an atom are residing. • Number in front: Shell/Principle energy level (Corresponds to the rows of the periodic table) • Letter: Sublevel or subshell. (s holds 2 electrons, p holds 6, d holds 10, and f holds 14) • Superscript: number of electrons currently in that sublevel. Remember, ions have different electron configurations then their base forms. Specifically, cations have fewer electrons, and anions have more electrons then their base configuration. NOTE: the elctron configurations of ions will resemble Noble gasses (Filled valance shell). In other words, mostly they should have 8 electrons (Octet Rule). Remember also that the very early atoms near He will only have 2. Determine the electron configurations of each of the following and determine the number of valance electrons: • Sodium ion Na: 1s22s22p6 8 valance electrons (Nobel gas like) • He He: 1s2 2 valance electrons (Nobel gas) • Li+ Li+: 1s2 (note the similarity to He, Li’s nearest Nobel gas) 2 v elec • S S: 1s22s22p63s23p4 6 valance electrons • O2- O: 1s22s22p6 8 valance electrons (Nobel gas like) • P P: 1s22s22p63s23p3 5 valance electrons • 5. Ar Ar: 1s22s22p63s23p6 8 valance electrons (Nobel gas) CHEM120 Exam 1 You re conducting a study on the effects of carrot consumption on blood pressure. you will be giving carrots to participants in your study and monitoring their blood pressure over several months B the amount of carrots consumed by the participant You have an isotope that has a mass number of 195 and contains 116 neutrons what isotope is this C Gold 79 Determine which ion has the ground state electron configuration of 1s22s22p63s23p6 D CA2+ Which of the following substances contain ionic bonds Li2O CaBr2 What is the name of the compound N2O3 dinitrogen dioxide which of the following species would you expect form intermolecular hydrogen bonds HF In an experiment you calculate that 6.50 gram of liquid has a volume of 2.50 ml B. Liquid X What is the mass of a 160 lb person using appropriate units? 72.73 kg You have purchased 0.5 gallons of a chemical to peer review an experimental procedure Correct answer is 1895 ml At a temperature of 14 degrees c X as having hydrogen bonding Intermolecular forces holding molecules together noting that hydrogen bonding procedures are a higher boiling point or that electrostatic bonding Non polar covalent compounds S8 O2 Match the following compounds with their molecular shapes Trigonal planar PF3 Linear CO2 Trigonal pyramidal BF3 Tetrahedral SF4 How many electrons Iron(II) ion 24 Oxide 10 Oxygen 8 Lithium Ion 23 An atom of Mg reacts with an atom of O Mg2+and O2- Gains electrons In a molecule that contains a polar covalent bond, electrons in this bond are Shared unequally The bond between two nitrogen atoms would be decribed as an: Triple covelent bond You have noticed that there has been a large amount of racoons invading your garden Develop a hypothesis and an experiment With a control group and predict the results of the experiment An experiment is conducted to study the effect of sprint water on the number of apples produced from the apple tree #of apples produced is the dependent variable A molecule forms from Na and F describe thus process in response to elerctron behavior charges and bond properties You have a bracelet 7.87 g/cm3 There are several stable isotopes of Mg as well as several ions of Mg possible 12 protons An ion has 4 neutrons 3 protons and 2 electrons what is the charge of the ion +1 What is the mass number of a silicon isotope with 15 neutrons 29