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- Refer to a periodic table. Which pair of elements do you expect to be most similar in their chemical properties? (LO 2.3) (a) K and Cu (b) O and Se (c) Be and B (d) Rb and Sr
Problem 1
- A compound containing sulfur and fluorine contains 8.00 g of S and 9.50 g of F. Which combination of S and F masses represents a different compound that obeys the Law of Mul-tiple Proportions? (LO 2.8) (a) 32.0 g of S and 38.0 g of F (b) 4.00 g of S and 4.75 g of F (c) 8.00 g of S and 10.5 g of F (d) 16.0 g of S and 57.0 g of F
Problem 4
- Which experiment and subsequent observation led to the discovery that atoms contain negatively charged particles, now known as electrons? (LO 2.10–2.12) (a) Oil is sprayed into a chamber and the speed at which the oil droplets fall is measured with and without an applied voltage. X rays in the chamber knock electrons out of air molecules. The electrons stick to the oil pro-ducing an overall negative charge on the drops. Adjusting the voltage changes the speed at which the negatively charged oil droplets fall. (b) When a high voltage is applied across metal electrodes at opposite ends of a sealed glass tube, a cathode ray is produced. The cathode ray is repelled by a negatively charged plate. (c) A radioactive substance emits alpha particles, which are directed at a thin gold foil. Most of the alpha par-ticles pass through the foil, but a few alpha particles are slightly deflected and some even bounce back toward the radioactive source. (d) The mass of different elements in a pure chemical com-pound are measured. Different samples of the compound always contains the same proportion of elements by mass.
Problem 5
- Which sample has the greatest mass? (LO 2.16) (a) 5.5 mol of C (b) 2.1 mol of S (c) 4.2 mol of Be (d) 0.52 mol of Ag
Problem 8
- How many atoms are present in 1.2 g of gold? (LO 2.16) (a) 2.5 * 1021 (b) 1.4 * 1026 (c) 7.2 * 1023 (d) 3.7 * 1021
Problem 9
Problem 10
Bromine has two naturally occurring isotopes; 79Br (mass of 78.918) and 81Br (mass of 80.916). If the atomic weight of bromine is 79.904, predict the mass spectrum of a sample of bromine atoms. (LO 2.17) (a)
(b)
(c)
(d)
Problem 11
The molecular illustration represents (LO 2.18) (a) a pure element (b) a mixture of two elements (c) a pure compound (d) a mixture of an element and a compound
- How many protons, neutrons, and electrons are in 107Ag+? (LO 2.21) (a) protons = 47, neutrons = 60, electrons = 46 (b) protons = 47, neutrons = 107, electrons = 48 (c) protons = 60, neutrons = 47, electrons = 47 (d) protons = 47, neutrons = 107, electrons = 46
Problem 13
Problem 14
What is the correct formula for sodium phosphate? (LO 2.24) (a) Na3PO4 (b) Na3P (c) NaPO4 (d) Na(PO4)2
Problem 35a
Is the red element on the following periodic table likely to be a gas, a liquid, or a solid?
Problem 35b
What is the atomic number of the blue element?
Problem 35c
What is the group number of the green, blue, and red elements?
Problem 35d
Name at least one other element that is chemically similar to the green element.
- The element indicated on the following periodic table is used in smoke detectors. Identify it, give its atomic number, and tell what kind of group it's in.
Problem 36
Problem 37a
Identify the three elements indicated on the periodic table, and give the group that they are in.
Problem 37c
Would you expect these elements to have similar or different chemical reactivity?
- Assume that the mixture of substances in drawing (a) undergoes a reaction. Which of the drawings (b)–(d) rep-resents a product mixture consistent with the law of mass conservation?
Problem 39
(b)
(c)
(d) - In the following drawings, red spheres represent protons, and blue spheres represent neutrons. Which of the draw-ings represent different isotopes of the same element, and which represents a different element altogether? (a)
Problem 40
(b)
(c) Problem 41a
Which of the following three drawings represents a neutral Na atom? (a) (b) (c)
Problem 41b
Which represents a Ca atom with two positive electrical charges (Ca2+)? (a)
(b)
(c)
Problem 41c
Which represents an F atom with one minus charge (F-)? (a)
(b)
(c)
Problem 42
In the following drawings, red and blue spheres represent atoms of different elements. Match the molecular pictures (a)–(c) with the following descriptions: (i) a pure substance consisting of a compound (ii) a pure substance consisting of an element (iii) a mixture of element
Problem 44b
Give molecular formulas corresponding to each of the following ball-and-stick molecular representations (red = O, gray = C, blue = N, ivory = H). In writing the formula, list the elements in alphabetical order. (b) Ethylene glycol (automobile antifreeze)
Problem 44c
Give molecular formulas corresponding to each of the following ball-and-stick molecular representations (red = O, gray = C, blue = N, ivory = H). In writing the formula, list the elements in alphabetical order. (c) Acetic acid (vinegar)
- How many elements are presently known? About how many occur naturally?
Problem 46
Problem 46a
What are the molecular weights of the following pharmaceuticals? (a) C33H35FN2O5 (atorvastatin, lowers blood cholesterol)
- Which element accounts for roughly 75% of the observed mass of the universe? Which four elements make up 95% of the mass of the human body?
Problem 47
- Look at the alphabetical list of elements inside the front cover. What are the symbols for the following elements? (a) Gadolinium (used in color TV screens) (b) Germanium (used in semiconductors) (c) Technetium (used in biomedical imaging) (d) Arsenic (used in pesticides)
Problem 48
- Look at the alphabetical list of elements inside the front cover. What are the symbols for the following elements? (a) Cadmium (used in rechargeable Ni-cad batteries) (b) Iridium (used for hardening alloys) (c) Beryllium (used in the space shuttle) (d) Tungsten (used in light bulbs)
Problem 49
- Look at the alphabetical list of elements inside the front cover. Give the names corresponding to the following symbols: (a) Te (b) Re (c) Be (d) Ar (e) Pu
Problem 50