Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
UNIT 2 EXTRA PROBLEMS FOR THE WEBSITE (Honors & Regents): Atomic Structure, Nuclear Chemistry , Nomenclature, and the Mole. [Note that the Regents and Honors courses are slightly different in unit 2. The questions which pertain to Regents are indicated (R)] 1. What is the approximate number of molecules in a drop of water which weighs 0.09 g? (R) [3.01 x 1021] 2. How many moles are present in 100. g quantities of each of the following? (a) calcium carbonate (b) H2O (c) hydrochloric acid (d) aluminum sulfate (R) [1; 5.55; 2.74; 0.292] 3. An unknown compound consists of 82.98% potassium and 17.02% oxygen. What is the empirical formula of the compound? (R) [K2O] 4. A compound subjected to analysis was found to have the following composition by mass: 69.96% carbon, 7.83% hydrogen, and 22.21% oxygen. If the molecular mass of the compound is 360 g/mol, what is its molecular formula? (R) [C21H28O5] 5. Calculate the percentage composition of aluminum sulfate.(R) [15.8% Al; 28.1% S; 56.1% O] 6. Calculate the percent by mass of each element in magnesium chloride.(R) [25.5% Mg; & 4.5% Cl] 7. When a piece of magnesium ribbon weighing 0.32 g is burned in oxygen, the resultant oxide weighs 0.53 g. What is the percentage composition of the oxide? [60.% Mg; 40.% O] 8. Natural chlorine is a mixture of isotopes. Determine its average atomic mass if 75.53% of the naturally occurring element is chlorine-35, which has a mass of 34.968, and 24.4% is chlorine-37, which has a mass of 36.956. [35.45 amu] 9. How many protons, neutrons, and electrons are in an atom of the following elements? a) boron, mass number 11 , b) krypton, mass number 84 , c) scandium, mass number 45 , d) potassium, mass number 39 [5,6,5; 36, 48, 36; 21, 24, 21; 19, 20, 19] 10. The mass number of an isotope of oxygen is 17. Write the name and symbol for this isotope. [oxygen-17; 178O] 11. What is an atomic mass unit? [1/12 the mass of the carbon-12 isotope] 12. An atom has 22 neutrons and 18 protons in its nucleus. What is the atomic number, mass number, and symbol of this element? [18, 40, Ar] 13. Name each of the following substances: (a) CaO (b) Ba3(PO4)2 (c) I2 (d) FeSO4 (e) Mg(OH)2 (f) NO2 (g) CuC2H3O2 (h) HClO4 (i) Cl2O (j) HgF2 (k) (NH4)2C2O4 (l) NO2[calcium oxide; barium phosphate; iodine; iron(II) sulfate; magnesium hydroxide; nitrogen dioxide; copper(I) acetate; perchloric acid; dichlorine monoxide; mercury(II) fluoride; ammonium oxalate; nitrite ion] 14. Write formulas for these compounds: (a) silver chloride , (b) aluminum carbide , (c) lithium hydride , (d) nitric acid , (e) ferric carbonate , (f) hypochlorous acid , (g) tin(IV) cyanide , (h) hydrocyanic acid, (i) potassium iodide , (j) calcium hydrogen carbonate , (k) carbon tetrachloride , (l) trisilicon tetranitride [AgCl; AlC3; LiH; HNO3; Fe2(CO3)3; HClO; SnCN4; HCN; KI; Ca(HCO3)2; CCl4; Si3N4] The following problems are for Honors only: 15. Determine the relative abundance of each isotope in naturally occurring gallium from the following data: average atomic mass of gallium is 69.72. Mass of 69Ga = 68.926 and mass of 71Ga = 70.925. [60% 69Ga; 40% 71Ga] 16. A chemist is given an unknown element X. She finds that it has an atomic mass of 210.197 amu, and consists of only two isotopes, 210X and 212X. If the masses of these isotopes are, respectively, 209.64 and 211.66 amu, what is the relative abundance of the two isotopes? [210X = 72.42%; 212X = 27.58%] 17. Complete the following nuclear equations: (a) 7N14 + 2He4 ---> 8O17 + (b) 1H3 ---> 3 9 4 12 30 30 2He + (c) 4Be + 2He ---> 6C + (d) 15P ---> 14Si + [1H1, -1e0, 0n1, +1e0 ] 18. 2.000 picogram (pg) of 33P decays by beta minus emission to 0.250 pg in 75.9 days. Find the half-life of 33P. [25.3 days] The following is an example of an Honors test: Multiple Choice: 1. Dalton's Atomic Theory included which idea? a) all atoms of all elements are the same size (b) atoms of different elements combine in one-to-one ratios only (c) atoms of the same element are always identical (d) individual atoms can be seen with a microscope (e) in a chemical reaction, atoms change into atoms of other elements 2. Select the correct statement about subatomic particles a) electrons are the heaviest subatomic particles and are negatively charged (b) protons are the lightest subatomic particles and are positively charged (c) neutrons have no charge and are the lightest subatomic particle (d) electrons, protons, and neutrons all have the same mass (e) the mass of a neutron nearly equals the mass of a proton 3. Isotopes of the same element have different a) mass numbers b) atomic numbers c) symbols d) numbers of electrons e) numbers of protons 4. Which two characteristics do radioisotopes have that makes them useful for medical diagnosis? a) long half-lives and quick elimination from the body b) long half-lives and slow elimination from the body c) short half-lives and quick elimination from the body (e) short half-lives and slow elimination from the body 5. Which pair of nuclei can undergo a fusion reaction? a) potassium -40 and cadmium -113 (b) zinc -64 and calcium -44 (c) uranium -238 and lead -208 (d) hydogen -2 and hydrogen -3 6. Which is the formula for magnesium sulfide? a) MgSO4 b) MgS2 c) MgS d) MnS 7. If element X is an alkali metal, what is the formula of its oxide? a) XO b) XO2 c) X2O d) X2O2 8. Which element forms more than one binary compound with chlorine? a) calcium b) potassium c) iron d) zinc 9. A radioactive element will lose the greatest amount of mass when it emits a) a neutron b) a proton c) a beta particle d) an alpha particle 10. In the equation: 2411Na ----> 2412Mg + X, X represents a) a neutron b) a proton c) a beta particle d) an alpha particle 11.The number of neutrons in the nucleus of an atom can be calculated by a) adding together the number of electrons and protons b) subtracting the number of electrons from the number of protons c) subtracting the number of protons from the mass number d) adding the mass number to the number of electrons 12. If an isotope undergoes beta emission: a) the mass number changes b) protons are given off c) the atomic number changes d) the number of neutrons remains the same 13. The most penetrating form of radiation is: a) alpha b) beta c) gamma d) visible 14. Nuclear fusion: a) takes place in the sun b) occurs when large nuclei fuse together c) produces hydrogen nuclei d) all of the above are true 15. Which of the following particles is needed to complete this reaction? a) 5525Mn + 21H ---> _______ + 210n a) 5627Co (b) 2725Mn (c) 5526Fe (d) 5824Cr 16. Which of these naturally occurring radioisotopes would be most useful in dating objects thought to be millions of years old? a) 14C: t1/2 = 5730 years (b) 40K: t1/2 = 1.28 x 109 years (c) 234Th: t1/2 = 25 days (d) 222Ra: t1/2 = 3.8 days 17. Which of these statements is not true? a) atoms of the same element can have different masses b) atoms of isotopes of an element have different numbers of protons c) the nucleus of a neutrl atom has a positve charge d) atoms are mostly empty space 18. Dalton theorized that atoms are indivisible and that all atoms of the same lement are identical. We now know that: a) Dalton's theories are correct b) atoms of a given element can have different numbers of neutrons c) atoms contain no smaller subatomic particles d) all atoms of a given element are not identical but they must all have the same mass 19. After 252 days, a 12.0 g sample of 42Sc contains only 1.5 g of the isotope. What is the half-life of 42Sc? a) 252 days b) 84 days c) 3 days d) 1.5 days 20. Which atom when combined with chlorine would most likely form a molecular compound? a) lithium b) calcium c) nickel d) phosphorus 21. An empirical formula: a) gives information about molecular structures b) shows the number and kinds of atoms in a molecule of a substance c) shows the simplest whole number ratio in which elements combine d) uses superscipts to show the number of each kind of atom in a molecule 22. What is the ionic charge on the manganese ion in the ionic compound manganese oxide written as MnO2? a) +2 (b) -2 (c) +4 (d) -4 23. The metals in Groups 1, 2, and 13: a) gain electrons when they form ions (b) all form ions with a -1 charge (c) lose electrons when they form ions (d) form only negative ions 24. A 10.3 g sample of NiO was formed from 8.1 g of nickel and 2.2 g of oxygen. What is the percent compositon of this oxide? a) 81% Ni and 22% O (b) 79% Ni and 21% O (c) 73% Ni and 27% O (d) none of these choices is correct 25. What percent of an original 20.0 g sample of 131I remains after 32 days? a) 50% b) 6.25% c) 12.5% d) 1.25% Problems: 26. a) One method for producing plutonium -238 is by bombarding uranium -238 with deuterons. This process produces neptunium -238 and another type of particle. The unstable neptunium then decays to form plutonium -238. Write balanced nuclear equations for this two step process. (b) With what particle would you bombard sulfur -32 to produce hydrogen -1 and phosphorus -32? Write the appropriate nuclear equation. (c) Complete the following nuclear equations: 87 37Sr ---> 8738Sr + _________ 230 92U ---> 42He + _________ 27. The two principal isotopes of copper are 63Cu and 65Cu. The atomic mass of Cu-63 is 62.9298 amu, and the atomic mass of Cu-65 is 64.9278 amu. determine the percent abundance of each isotope if the average atomic mass of copper is 63.546 amu. 28. Refer to the graph below (get diagram from Ms. Fed) which represents the radioactive decay of strontium -90. a) Based on the graph, what is the half-life of strontium -90? b) How much of the original sample would remain after about 140 years? c) If an original sample of strontium -90 contains 300.0 g, how much of the original sample has decayed after 84 years? 29. Complete the table below by supplying the missing information - either formula or name: .................NAME ....................................................FORMULA potassium bromate ..............................................________________ ______________ ...............................................H2SO3(aq) dinitrogen pentoxide ............................................________________ periodic acid .......................................................________________ hydrosulfuric acid ................................................________________ _____________ ................................................NaHCO3 tin (II) fluoride .................................................... ________________ potassium permanganate .................................... ________________ _____________ ............................................... HNO3(aq) _____________ ............................................... CuO 30. Each term in column A refers to a nuclear reactor. Match each term in column A with the appropriate description or substance in column B. ........Column A .............................................................Column B a. moderator ___________ ...........................................1. water b. control rods __________ ...........................................2. lead or concrete c. breeder reactor ________ ..........................................3. slows down neutrons d. shielding _____________ ...........................................4. cadmium e. coolant ______________ ........................................... 5. uranium 235 f. fuel rods _____________ ............................................ 6. produces plutonium -239 Answers: 1 c, 2 e, 3 a, 4 c, 5 d, 6 c, 7 c, 8 c, 9 d, 10 c, 11 c, 12 c, 13 c, 14 a, 15 c, 16 b, 17 b, 18 b, 19 b, 20 d, 21 c, 22 c, 23 c, 24 b, 25 b. 26. 238U92 + 21H ---> 23893Np +210n ;23893Np ---> 23894Pu + 0-1e 27. 69% Cu -63; 31% Cu -65 28. (a) 30 years (b) 0.31 g (c) 262.5 g has decayed 29. NAMES : sulfurous acid ; sodium hydrogen carbonate ; nitric acid ; copper(II) oxide. FORMULAS : KBrO3 ; N2O5 ; HIO4 ; H2S ; SnF2 ; KMnO4. 30. a) 3 b) 4 c) 6 d) 2 e) 1 f) 5