MidtermChem110F2010FormatB

MidtermChem110F2010FormatB - Page 1 of 7 ExamI Format B...

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Page 1 of 7 ExamI Format B Instructor: Vahid Eskandari Chemistry 110 (Fall 2010) Midterm Nov 10 th 2010 (2.5 pts each question) Exam Format B 1. One of the main features of Dalton's atomic theory no longer considered valid is: All atoms of each element are identical in every respect. Which of the following is the best explanation of why this feature is no longer considered valid? a. The existence of isotopes b. Mass is conserved in a chemical change c. Nearly all of the mass of an atom is concentrated in the nucleus d. The total charge of the electrons of an atom exactly balances the positive charge of the nucleus e. The planetary model of the atom has been shown to be incorrect 2. Which group of elements contains only non-metals? A) P, As, Se B) Mg, Ca, Sr C) Cl, Ar, K D) C, S, I E) V, Cr, Mn 3. Which of the following statements is false ? a. The atomic mass unit is exactly 1/12 of the mass of a carbon-12 atom b. Both protons and neutrons have atomic masses very close to 1 amu c. A carbon-12 atom with six electrons has a mass of 12.6 amu d. The atomic mass of an element is the average mass of the atoms of an element compared to an atom of carbon-12 at exactly 12 amu e. To find the atomic mass of an element, you must know the atomic mass of each isotope and the fraction of each isotope in a sample 4. Two natural isotopes exist for an unknown element. 51.83% of the atoms have a mass of 106.90509 amu, and the remainder has a mass of 108.9047 amu. Calculate the atomic mass. a. 52.46 amu b. 55.41 amu c. 106.90509 amu d. 107.87 amu e. 108.9047 amu 5. What is the formula of barium hydroxide octahydrate? a. Ba(OH) 2 • 8 H 2 O b. Ba(OH) 2 • 6 H 2 O c. B(OH) 3 • 8 H 2 O d. B(OH) 3 • 6 H 2 O e. B(OH) 3 + 8 H 2 O( ) 6. What are the formulas of the compounds magnesium sulfate and lithium bromite? a. Mg 3 (SO 3 ) 2 , LiBr b. MgSO 3 , LiBrO 3 c. MgSO 3 , Li 2 BrO 3 d. MgSO 4 , LiBrO 2 e. MgSO 4 , Li 2 BrO 30
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Page 2 of 7 ExamI Format B 7. How many atoms of each element are in a formula unit of magnesium phosphate? a. 3 magnesium atoms, 2 phosphorus atoms, 8 oxygen atoms b. 2 magnesium atoms, 3 phosphorus atoms, 12 oxygen atoms c. 1 magnesium atom, 1 phosphorus atom, 4 oxygen atoms d. 2 magnesium atoms, 1 phosphorus atom, 4 oxygen atoms e. 1 magnesium atom, 2 phosphorus atoms, 8 oxygen atoms 8. Calculate the percentage composition of calcium chlorate Ca(ClO 3
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MidtermChem110F2010FormatB - Page 1 of 7 ExamI Format B...

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