Test Review Periodic Trends and The Mole

Transcription

1 Test Review Periodic Trends and The Mole The Mole SHOW ALL WORK ON YOUR OWN PAPER FOR CREDIT!! 1 2 (NH42SO2 %N 24.1 %H 6.9 %S 27.6 %O 41.3 % Al %C 35.3 %H 4.4 %O 47.1 Al(C2H3O How many moles are present in 34 grams of Cu(OH2? (0.35 moles 4 How many oxygen atoms are found in moles of Fe2(CO33? (1.1X How many grams are there in 3.4 x 1024 molecules of NH3?(96 grams 6 How much does 4.2 moles of Ca(NO32 weigh?(690 grams 7 How much would 100 L of water vapor weigh in grams? (80 grams 8 Write the molecular formulas of the following: A compound with an empirical formula of C2OH4 and a molar mass of 88 grams per mole. (C4O2H8

2 9 Write the molecular formulas of the following :A compound with an empirical formula of C 4 H 4 O and a molar mass of 136 grams per mole. (C 8 H 8 O 2 10 What is the empirical formula for a compound which contains g of iron, g of sulfur and g of oxygen? (FeSO 3 11 Find the empirical formula if a compound is analyzed and found to contain 83.4% Mercury, 6.6% Sulfur, 9.96% Oxygen. (Hg 2 SO 3 12 What s the empirical formula of a molecule containing 65.5% carbon, 5.5% hydrogen, and 29.0% oxygen?(c 3 H 3 O 13 If the molar mass of the compound in problem 12 is 110 grams/mole, what s the molecular formula? (C 6 H 6 O 2 14 What s the empirical formula of a molecule containing 18.7% lithium, 16.3% carbon, and 65.0% oxygen? (Li 2 CO 3

3 15 For the hydrate Na 2 SO 4 10H 2 O calculate the percent of water (by mass in the hydrate (55.9% 16 A chemists heats a sample of hydrated lithium nitrate which weighs 170 grams and finds, after heating that it weighs 95.3 grams. Find the correct formula of the hydrate and name it. (LiNO 3 3H 2 O Periodic Trends 17 Arrange each group of elements in order of increasing ionization energy. a. F, Br, I, Cl I! Br! Cl! F b. Ga, Al, Tl, B Tl! Ga! Al! B c. Al, Si, Cl, S Al! Si! S! Cl 18 For each group of elements, choose the one with the largest atomic radius. a. He, Rn, Xe, Ar Rn b. As, N, P, Bi Bi c. Ba, Hf, Os, Hg Ba 19 Rank the following elements by increasing atomic radius: carbon, aluminum, oxygen, potassium. From smallest to largest: oxygen < carbon < aluminum < potassium 20 Rank the following elements by increasing electronegativity: sulfur, oxygen, neon, aluminum. From smallest to largest: neon < aluminum < sulfur < oxygen

4 21 Why does fluorine have a higher ionization energy than iodine? It is harder to pull electrons off of fluorine because fluorine is smaller in size thus the electrons have a stronger attraction to the nucleus resulting in a higher electronegativity than iodine. 22 Why do elements in the same family generally have similar properties? Because they have similar electron configurations and the same number of valence electrons. Because valence electrons are responsible for most of the chemistry we observe, this similarity causes the properties of the elements to also be similar. 23 What happens to the size of an atom when it becomes an anion? Why? Anions (negatively charged The atom has GAINED electrons to become negatively charged (more electrons than protons They are LARGER than the neutral atom of the same element because The protons in the nucleus cannot pull in the increased Negative charge and the added electrons are repelling each other, pushing them farther apart 24 What happens to the size of an atom when it becomes an cation? Why? Cations (positively charged The atom has LOST electrons to become positively charged (more protons than electrons They are SMALLER than the neutral atom of the same element because the valence electrons are lost, along with the entire outer shell. 25 Define each of the following periodic trends, identify their trends along a period and down a group, and why this happens: a. Atomic Radius a. distance from the center of an atom's nucleus to the edge of its electron cloud. b. Period trend - decreases across a period because of the increase in positive charge of nucleus (more p+ added creates a greater pull on the e towards nucleus while the new e are added within same energy level c. Group Trend - increases down a group because e are added to higher energy levels, farther from nucleus, making radius larger b. Ionization Energy a. energy required to overcome nuclear attraction and remove one valence electron b. ionization energy decreases down a group because The farther away from the nucleus an electron is, the easier it is to remove because the positive charge of the proton has less hold on the negative charge of the electron.

5 c. Ionization energy increases across a period because Elements on the right of the chart want to take electrons, so they do not want to donate any. Elements on the left of the chart would prefer to give up their electrons so it is easy to remove them. c. Electronegativity a. tendency of an atom to attract e towards its nucleus when chemically combined (bonded with another element b. electronegativity decreases down a group because Elements near the top of the period table have few electrons, so every electron is a big deal. Elements near the bottom of the chart have so many electrons that loosing or taking an electron is not as big a deal. c. electronegativity increases across a period because Elements on the left of the period table would rather give electrons away than take another atom's electrons. Elements on the right side of the period table only need a few electrons to complete the octet, so they have strong desire to take another atom's electrons.