General Chemistry 145 (Spring, 2018) Exam-10/132018); 90 min, Total Points 100pt
ID: 1085061 • Letter: G
Question
General Chemistry 145 (Spring, 2018) Exam-10/132018); 90 min, Total Points 100pts (6) Which one of the following is an example of a chemical change? Name a) Sugar dissolves in water b) Water in an open container evaporates c) The ice cube in your drink melts d) Liquid propane in a gas grill burns in a flame 7) Which of the following pairs has the same number of electrons a) Ca? and Mg2 b) Mg and O c) Na and Na d) Fe and Fe protons, has An atom of the most common isotope of gold, "Au, neutrons, and (8) electrons. a) 197,79, 118 b) 79, 118, 79 c) 79, 197, 197 d) 79, 118, 118 (9) What statement best describes the atomic weight of an element? a) Atomic weight is the sum of the masses of the isotopes multiplied by their relative abundances b) Atomic weight is the product of the relative abundances masses. c) Atomic weight is the masses of the isotopes less their relative abundances. d) Atomic weight is the sum of the masses of the isotopes. (10) Which pair of elements would you expect to exhibit the greatest similarity in physical and chemical properties? a) B, N b) Rb, I c) Ca, Br d) Ne, Ar 11) Which one of the following will ocur as diatomic molecules in elemental form? a) boron b) lithium c) nitrogend) argon ) Which compounds do not have the same empirical formula? (12) c) CO, CO d) CHO, CH.OExplanation / Answer
6.The answer is D.
chemcial changes means composition of compound is changes during the process.
C3H8 + 5 O2 ----------------- 3 CO2 + 4H2O
7.The answer is B
Mg+2 and O-2 has the same number of electrons.
Mg --------------- Mg+2 + 2e-
12 10
O + 2e- -------------- O-2
8 10
so Mg+2 and O-2 has contains 10 electrons,
8. The answer is B
Au-197 contains
atomic number of Au = 79
atomic number = number of protons = number of electrons= 79
number ofneutrons= mass number - number of protons = 197-79 = 118.
9.The answer is A
10.The answer is D
The elements Ne and Ar are the same group elemnts.
The elements which are present in the same group having same phisical and chemical properties due to same outermost electronic configaration. ns2np6
11.The answer is C
Nitrogen exists as diatomic molecule. N2
12.The answer is C
CO and CO2 have different emperical formula
emperical formula represents the simplest ratio of the atoms of an element ina compound
for example C6H6 and C2H2 has the same emperical formula CH.
13.The answer is A
MnF3
manganse exhibit 3+ state because F exhibits -1 state.
14.the answer is D
Ca+2 and PO4-3 -------------- Ca3(PO4)2
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