i need the solution FINAL EXAM EM 30A 18) When 85.0 g of CH4 are mixed with 160.
ID: 696661 • Letter: I
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i need the solution
FINAL EXAM EM 30A 18) When 85.0 g of CH4 are mixed with 160. g of O2 the limiting reactant is CH4 + 2O2 CO2 + 2H2O A) CH4. B) 02 C) CO2 D) H20 Answer: B 19) A reaction that releases energy as it occurs is classified as a(n) A) endothermic reaction B) exothermic reaction C) oxidation-reduction reaction. D) catalyzed reaction. E) decomposition reaction. Answer: B 20) Choose the best electron-dot structure for OCI2. B) Answer: E 21) The strongest interactions between molecules of HCl are A) ionic bonds. B) covalent bonds. C) hydrogen bonds D) dipole-dipole interactions E) dispersion forces. Answer: D shape 22) The carbon tetrachloride molecule, CCl4, is has pyramidal shape. B) a nonpolar molecule with polar bonds; and has tetrahedral sha C) a nonpolar molecule with nonpolar bonds; and has square planar shape. D) a polar molecule with nonpolar bonds; and has linear shape. E) a polar molecule with ionic bonds, and has tetrahedral shape pe Answer: BExplanation / Answer
18)
The equation is
CH4 + 2O2 ------------> CO2 + 2H2O
85g/16g/mol 160g/32g/mol 0 0 initial moles
= 5.3125 = 5.0
Calculation of limiting reagent
find the ratio of actual moles/ stoichiometric coefficient for each reactant , which has smaller ratio that is the limiting reagent
Ratio 5.3125/1 for CH4 = 5.3125
for O2 = 5.0/2 = 2.5
Thus the ratio required is less for O2 hence it is the limiting reagent
19) exothermic reaction is the one in which heat energy is liberated due to the reaction.
20) the best electron dot structure should confirm to the rules of Lewis structures like O can have maxium 3 covalents bonds, N and C can have a maxiumum of 4 covalent bonds.
The structures with all atoms having octet are more stable.
Thus E follows both of them.
21)Hydrogen chloride is apolar covalent molcule not ionic.
Thus it has dipole (H with partial positive charge and Cl with partial negative charge which are called poles).
Thus the interaction between Hcl are dipole-dipole interactions.
22) CCl4 is covalent molcule with C as central tom and has sp3 hybrdization.
thus the molecule is tetrahedral in shape.
Each C-Cl bond is polar due to the electronegativity difference between C and Cl. that is each bond is polar.
HOwever the molecule is non-polar as the measured dipole moment (a measure of polarity ) is the vector sum of bond moments and they cancel each other as the molecule is symmetric.
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