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Some more Regents Chemistry practice…. What is the empirical formula of C 3 H 6 ?. A: CH. C: CH 3. B: CH 2. D: CH 6. Empirical formula is the simplified version of a molecular formula… C 3 H 6 – divide by greatest common factor (3) to get CH 2. B.
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What is the empirical formula of C3H6? A: CH C: CH3 B: CH2 D: CH6
Empirical formula is the simplified version of a molecular formula…C3H6 – divide by greatest common factor (3) to get CH2 B
The name of the compound KClO2, is potassium A: chlorine oxide C: chlorate B: chlorite D: perchlorate
ClO2– is a polyatomic ion since there is more than one capital letter…go to Table E and keep it as is B
What is the percent by mass of carbon in HC2H3O2(gram-formula mass is 60)? A: 12 / 60 * 100 C: 24 / 60 * 100 B: 60 / 24 * 100 D: 60 / 12 * 100
Table T:% comp by mass = part / whole * 100Since there are TWO carbon atoms…it is 24 / 60 * 100 C
What is the mass of 6.5 moles of CO2 (g)? A: 44 g C: 0.15 g B: 6.8 g D: 286 g
Determine the gram formula mass of CO2 (12 + 2(16) = 44g/mol)6.5 mol * 44 g/mol= 286 g D
The measure of the attraction for electrons in a chemical bond is C: attractivity A: ionization energy B: atomic radius D: electronegativity
Electronegativity…you can look up those values in Table S.Ionization energy is energy required to remove an electron. D
Given the equation:H2 + Cl2→ 2 HClHow many moles of HCl will be produced when 3 moles of H2 is completely consumed? A: 3 moles C: 6 moles B: 2 moles D: 0.7 moles
H2 + Cl2 → 2 HClSet up a ratio:eqn: 1 2 =?: 3 x C
What type of bond exists between an atom of carbon and an atom of fluorine? A: ionic C: polar cov. B: metallic D: nonpolar cov.
Has to be covalent because two nonmetals…Look up electronegativity values in Table S to see to that the difference is greater than 1.Polar: e- shared UNequallyNonpolar: e- shared equally C
Which is held together by metallic bonds? A: NaCl C: CO B: Fe D: Br2
The primary forces of attraction between water molecules in H2O are A: ionic C: molecule-ion B: hydrogen D: van der Waals
When H is bonded to F, O, or N, the intermolecular force is hydrogen bonding…H2O and NH3 are great examples of polar molecules and hydrogen bonding. B
Which substance contains nonpolar covalent bonds? A: H2 C: Ca(OH)2 B: H2O D: CaO
Covalent – must be two NONMETALSNonpolar – electrons shared equally…electronegativity difference less than 1. A
What describes the electron dot structure of CaCl2? A: brackets without charges C: brackets with charges B: no brackets, no charges D: no brackets, but charges
C CaCl2 is ionic (metal and nonmetal) so needs brackets AND charges… +2 -1 -1 [ ] [ ] [ ] Cl Ca Cl (gained 1 e-) (gained 1 e-) (lost 2 e-)
Which statement best describes the following reaction?Cl + Cl → Cl2 + energy A: bond formed & energy released C: bond formed & energy absorbed B: bond broken & energy released D: bond broken & energy absorbed
Two reactants become one product…bond is formedEnergy is on the product side…energy is released A
The modern model of the atom shows that electrons are A: orbiting nucleus in fixed paths C: found in regions called orbitals B: combined with neutrons in the nucleus D: located in a solid sphere covering nucleus
Modern model of atom = wave-mechanical model ORelectron cloud model…orbital = probable locations of e- C
What is atomic number of an element that has 6 protons and 8 neutrons? A: 6 C: 8 B: 2 D: 14
What is the total number of protons contained in the nucleus of a carbon-14 atom? A: 6 C: 12 B: 8 D: 14
The “14” in carbon-14 represents the mass number (protons + neutrons). If the atom is carbon…look up its atomic number. A
Which of these elements has an atom with the most stable outer electron configuration? A: Ca C: Na B: Cl D: Ne
Look for the noble gases in group 18…They have full valence shells. (2 e- for He, 8 e- for the rest) D
What is the nuclear charge of an iron atom? A: +30 C: +56 B: +26 D: +82
Protons and neutrons are in nucleus. Protons are positive and neutrons are neutral...making the charge on the nucleus positive. Look up atomic number of iron = 26. B
How many electrons are in the outermost principal energy level of an atom of bromine in the ground state? A: 35 C: 2 B: 7 D: 8
Look up the number of valence e-…Electron config: 2-8-18-7Valence e- are last number = 7…Group 17 has 7 valence e-. B
Which electron configuration is correct for a sodium ion? A: 2-7 C: 2-8 B: 2-8-1 D: 2-8-2
Na electron config as an ATOM is2-8-1It is in group 1 and will lose its 1 valence e- to become stable. C
The nucleus of which atom contains 48 neutrons? 32 A: S 16 85 C: Rb 37 112 D: Cd 48 48 B: Ti 22
Mass number is top number = protons + neutronsAtomic number is bottom number = number of protons(protons + neutrons) – (protons) = NEUTRONS C
When an atom loses an electron, the atom becomes an ion that is A: (+) and larger C: (+) and smaller B: (-) and larger D: (-) and smaller
Losing e-… (+) charge (look at oxidation state)When you lose weight, for example, you become smaller…the same goes for atoms & ions. C
Spectral lines of elements are caused when electrons in an excited state move from A: low to high energy levels, absorbing energy C: low to high energy levels, releasing energy B: high to low energy levels, absorbing energy D: high to low energy levels, releasing energy
An atom absorbs energy…electron jumps to higher energy level.(excited state)When the electron falls back to a lower energy level, energy is released in the form of light.(back to ground state) D
What happens when NaCl is dissolved in water? A: Na+ ions attracted to O atoms of water C: Cl- ions attracted to O atoms of water B: Na+ ions are repelled by the O atoms of water D: Cl- ions are repelled by the H atoms of water
Oxygen atoms have a partial negative charge so the Na+ ions are attracted to that side of the water molecule. A
According to Table G, which solution at equilibrium contains 50 g of solute per 100 g of water at 75˚C? A: unsaturated solution of KCl C: unsaturated solution of KClO3 B: saturated solution of KCl D: saturated solution of KClO3
Saturated solution is when falls right on the curve.Go over to 75 degrees and up to 50 g of solute. B
Which compound is least soluble in 100 g of water at 40˚C? A: SO2 C: KClO3 B: NaCl D: NH4Cl