Question

Question 1 (10 points)
1. What is the molar mass of Ca(ClO4)2? g/mol (Round ans. to nearest 1st decimal place)

2. how many moles are in 597.5 g of Ca(ClO4)2? mol (Round ans. to nearest 1st decimal place)



Use these molar masses for calculations: Ca = 40, Cl =35.45, O =16

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Question 2 (4 points)
Moles and moles: How many moles of carbondioxide gas is produced 6.80 moles of C3H4O2 is combusted in this reaction?

C3H4O2 + 3O2 → 3CO2+ 2H2O

(Molar mass of C = 12.011 g/mol, H = 1.008 g/mol, O = 15.999 g/mol)

a
3.40 mol
b
13.6 mol
c
2.27 mol
d
20.4 mol
Question 3 (4 points)
The table shows a chemical equation and the dimensional analysis used by a student to calculate the number of moles of Ba3N2 required to produce 9.2 moles of Ba(OH)2.

Student's Dimensional Analysis:
Chemical Equation Dimensional Analysis
Ba3N2 + 6H2O → 3Ba(OH)2 + 2NH3
= 9.2 mol of Ba(OH)2 x 3 mol of Ba(OH)2

1 mol of Ba3N2



What is the error in the dimensional analysis?

a
3 mol of Ba(OH)2 should be replaced with 1 mol of Ba(OH)2
b
3 mol of Ba(OH)2 and 1 mol of Ba3N2 should be interchanged
c
1 mol of Ba3N2 should be replaced with 3 mol of Ba3N2
d
9.2 mol of Ba(OH)2 and 1 mol of Ba3N2 should be interchanged
Question 4 (14 points)
How many grams of CaCl2 are needed to react completely with 6.2 mol of AgNO3 ? (Fill in the blank with the correct answer. Round any calculated answer to nearest 1st decimal place.

2 AgNO3 + CaCl2 → 2AgCl + Ca(NO3)2



The correct set up for the calculation:




= g of g CaCl2 (Final answer)

= 6.2 mol AgNO3 X mol / mol X g CaCl2 / mol CaCl2




Use these molar mases for your calculations: Ag = 107, Cl =35.45 , N =14, O= 16 , Ca =40

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Question 5 (12 points)
Moles and moles: How many moles of carbondioxide gas is produced 20 g of C3H4O2 is combusted in this reaction?

C3H4O2 + O2 → CO2 + H2O

1. find the Mole ratio of balanced equatoion: : : : (blank # 1 to 4)



2. What is the molar mass of C3H4O2 : g/mol (Blank # 5, only write the number value, not units, round to nearest 1st decimal)

(Molar mass of C = 12 g/mol, H = 1.0 g/mol, O = 16 g/mol)



3. calculate using dimensional analysis the moles of carbondioxide gas is produced 20 g of C3H4O2 : mol (blank # 6, only write the number value, not units, round to nearest 1st decimal)



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Answer 1

Question 1
Blank 1: 238.9 g/mol
Blank 2: 2.5 mol

(Work: M = 40 + 2(35.45) + 8(16) = 238.9 g/mol; moles = 597.5 / 238.9 = 2.5 mol)

Question 2
Answer: d (20.4 mol)

(3 mol CO2 per 1 mol C3H4O2 → 3 × 6.80 = 20.4 mol)

Question 3
Answer: b

(The student inverted the conversion factor; 3 mol Ba(OH)2 and 1 mol Ba3N2 should be interchanged.)

Question 4
Set-up and blanks:
= 6.2 mol AgNO3 × (1 mol CaCl2 / 2 mol AgNO3) × (110.9 g CaCl2 / 1 mol CaCl2) = 343.8 g CaCl2

Blank 1: 6.2
Blank 2: mol AgNO3
Blank 3: 1 mol CaCl2
Blank 4: 2 mol AgNO3
Blank 5: 110.9 g CaCl2
Blank 6: 1 mol CaCl2
Blank 7: 343.8 g CaCl2

(Work: molar mass CaCl2 = 40 + 2(35.45) = 110.9 g/mol; required moles CaCl2 = 6.2 × 1/2 = 3.1 mol; mass = 3.1 × 110.9 = 343.8 g)

Question 5
Blank 1: 1
Blank 2: 4
Blank 3: 3
Blank 4: 2
Blank 5: 72.0
Blank 6: 0.8

(Work: balanced: C3H4O2 + 4 O2 → 3 CO2 + 2 H2O. Molar mass C3H4O2 = 3(12)+4(1)+2(16)=72.0 g/mol. Moles CO2 = 20 g × (1 mol /72.0 g) × (3 mol CO2 /1 mol) = 0.8333 → 0.8 mol rounded)