Question

9) What is the total number of atoms in 0.139 mol of Fe(OH263-? A) 19.0 B) 2.64 98.37. 1022 D) 1.59. 1024 E) 184. 1024 10) How many carbon atoms are there in 52.06 g of carbon dioxide? A) 8.648.10-23 B) 3.134 x 1025 C) 7.122 1023 D) 5.206 X 1024 E) 1.424 . 1024 11) A nitrogen oxide is 63.65% by mass nitrogen. The molecular formula could be A) NO B) NO2 CN204 D) N20 E) either NO2 or N20 12) Which hydrocarbon pair below has identical mass percentage of C? A) CH4 and C3H4 B) C3H4 and C3H6 C) C2H4 and C4H2 D) C2H4 and C3H6 E) none of the above 13) Propane (C3H8) reacts with oxygen in the air to produce carbon dioxide and water. In a particular experiment, 38.0 grams of carbon dioxide are produced from the reaction of 22.05 grams of propane with excess oxygen. What is the % yield in this reaction? A) 66.0 B) 94.5 38.0 E) 86.4 14) Aqueous solutions of a compound did not form precipitates with Cl-. Br.l.S04. CO3- PO43-OH-, or S2- This highly water-soluble compound produced the foul-smelling gas H2S when the solution was acidified. This compound is A) AgNO3 B) Pb(NO3) 2 C )Li2C03D ) (NH4)2S E) KB ID) the net ionic equation for formation of an aqueous solution of Nily accompanied by evolution of CO2 gas via mixing solid NiCO3 and aqueous hydriodic acid is A) NICO3(s)+1- (aq) -- 2H20 (1) + CO2(g) + Ni2+ (aq) + HI (aq) B) NiCO3 (s) + 2H1 (aq) -- 2H20 (1) + CO2(g) + Nil2 (aq) NICO3 (s) + 2HI (aq) - H20 (1) + CO2(g) + Ni2+ (aq) + 21- (aq) D) NICO3 (s) + 2H+ (aq) -- H20l).CO2 (s). Ni2+ (aq) E) 2NICO3(-) + HI (aq) + 2H2O(l) + CO2 (g) + 2N12+ (aq)

Answer 1

9)

1 mol of Fe(OH2)6 3+ has 19 atoms

So,

Mol of atoms = mol of compound * 19

= 0.139 * 19

= 2.641 mol

use:

number of atoms = number of moles * Avogadro’s number

= 2.641 * 6.022*10^23 atoms

= 1.59*10^24 atoms

Answer: D

10)

Molar mass of CO2,

MM = 1*MM(C) + 2*MM(O)

= 1*12.01 + 2*16.0

= 44.01 g/mol

mass(CO2)= 52.06 g

use:

number of mol of CO2,

n = mass of CO2/molar mass of CO2

=(52.06 g)/(44.01 g/mol)

= 1.183 mol

use:

number of molecules = number of mol * Avogadro’s number

number of molecules = 1.183 * 6.022*10^23 molecules

number of molecules = 7.122*10^23 molecules

Count of each element in compound is:

{C=1, O=2}

Total number of C atoms in 1 molecule = 1

use:

number of C atoms = number of molecules * Total number of C atoms in 1 molecule

= 7.122*10^23 * 1

= 7.122*10^23

Answer: C

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