Sem 2- (6 week 1) Flashcards
Balance the following equation.
___Mg + ___O2 –>___MgO
2,2,2
2,1,2
1,1,2
The equation is already balanced.
2,1,2
If the reaction below begins with 5 grams of magnesium and produces 12 g of magnesium oxide, how much oxygen was used in the reaction?
____Mg + ____O2 –> ____MgO
7 g
17 g
60 g
2.5 g
7 g
Balance the following equation:
C2H4 + O2 –> CO2 + H2O
1, 1, 2, 2
1, 3, 2, 2
2, 6, 4, 4
1, 3, 2, 2
The equation is balanced: 2Fe + 3Cl2 –> 2FeCl3
True
False
True
The following equation is balanced: KI + Pb(NO3)2 –> 2KNO3 + PbI2
True
False
False
Balance the following equation by filling in the blanks.
H2SO4 + NaOH H2O + Na2SO4
1, 2, 2, 1
Which of the following represents the balanced the equation for the following reaction:
Hydrochloric acid reacts with lithium hydroxide to produce lithium chloride and water.
HCl + LiOH –> LiCl + H2O
HLi + ClOH –> LiOH + HCl
2HCl + LiOH –> LiCl + H2O
LiCl + H2O –> HCl + LiOH
HCl + LiOH –> LiCl + H2O
Balance the following equation by filling in the blanks.
MgBr2 + Fe3P2–> Mg3P2 + FeBr2
3 MgBr2 + Fe3P2–> Mg3P2 + 3 FeBr2
Balance the following equation by filling in the blanks.
CaCO3 + HCl –> CO2 + H2O + CaCl2
CaCO3 + 2 HCl –> CO2 + H2O + CaCl2
Balance the following equation by filling in the blanks.
Al2O3 + K –> K2O + Al
Al2O3 + 6 K –> 3 K2O + 2 Al
How many moles are in 34.4 g of water, H2O?
- 91 mol
- 02 mol
- mol
- 71 x 10^-23 mol
1.91 mol
How many grams are in 0.0430 moles of carbon dioxide, CO2?
- 000980 g
- 20 g
- 89 g
- 60 x 10^22 g
1.89 g
On average, a human being needs approximately 445 grams of O2 in a day. How many molecules of O2 are required to meet this requirement?
- 57 x 10^27 molecules
- 37 x 10^24 molecules
- 31 x 10^-23 molecules
- 67 x 10^25 molecules
8.37 x 10^24 molecules
How many moles are in 3.2 x 10^22 particles of K2CO3?
- 9 x 10^46 mol
- 4 x 10^24 mol
- 3 x 10^20 mol
- 053 mol
0.053 mol
A necklace is found to have 5.43 x 10^19 atoms of gold, Au. How many grams of gold are in the necklace?
- 0178 g Au
- 07 x 10^22 g Au
- 02 x 10^-5 g Au
- 44 x 10^45 g Au
0.0178 g Au
How many atoms of silver are in a ring with a mass of 4.5 grams?
- 042 atoms
- 7 x 10^24 atoms
- 9 x 10^26 atoms
- 5 x 10^22 atoms
2.5 x 10^22 atoms
How many moles are in 6.24 x 10^32 molecules of methane (CH4)?
- 00 x 10^34mol
- 89 x 10^31 mol
- 04 x 10^9 mol
- 78 x 10^56 mol
1.04 x 10^9 mol
How many moles will be needed if a chemist is trying to create 15.5 grams of K2SO4?
- 70 x 10^3 mol
- 0890 mol
- 33 x 10^24 mol
- 57 x 10^-23 mol
0.0890 mol
How many particles are in 0.00345 moles of CaCl2?
- 08 x 10^21 particles
- 73 x 10^-27 particles
- 383 particles
- 12 x 10^-5 particles
2.08 x 10^21 particles
A jewelry factory has 1.23 moles of excess silver from the creation of a new bracelet. What is the mass of this excess silver? 7.41 x 10^23 g 2.04 x 10^-24 g 133 g 0.0114 g
133 g
What are the coefficients for the equation below when it is correctly balanced?
Ca(OH)2 + HCl –> CaCl2 + H2O
1, 2, 1, 2
2, 1, 2, 1
1,2,1,1
1,1,1,2
1, 2, 1, 2
What is the correct coefficient for O2 when the following equation is correctly balanced?
C3H8 + O2 –> CO2 + H2O
3
5
4
1
5
If 53.5 g of C3H8 are burned in the presence of 15.0 g of oxygen to produce 23.3 g of CO2, how many grams of water will be produced?
C3H8 + O2 –> CO2 + H2O
- 8 g
- 2 g
- 2 g
- 8 g
45.2 g
What are the coefficients for the equation below when it is correctly balanced?
NaHCO3 + HC2H3O2–> NaC2H3O2 + CO2 + H2O
2, 1, 2, 1,1
1, 2,1,2,2
2, 1, 2,1,2
1,1,1,1,1
1,1,1,1,1
What is the correct coefficient for O2 when the following equation is correctly balanced?
Al2O3 –> Al + O2
4
3
2
1
3
What is the percent composition of an unknown hydrocarbon that is found to contain 21.7 grams of carbon and 4.85 grams of hydrogen?
What is the percent of Carbon?
- 9 %
- 1 %
- 5 %
- 5 %
81.9 %
Calcium carbonate (CaCO3) is a common ingredient found in antacids. What is the percentage of oxygen?
- 0 %
- 0 %
- 0 %
- 0 %
48.0 %
The percent of hydrogen in Al(OH)3 is ________.
Round your answer to three significant figures. Include only numbers in your answer.
Molar mass of Al(OH)3 = 26.98 + (3 mol O x 15.999) + (3 mol H x 1.008) = 78.001 g /mol
% H = [(3 mol H x 1.008) / 78.001] x 100 = 3.877%
Answer is 3.88%
The percent of carbon in methane (CH4) is ____.
- 9
- 1
- 1
- 5
74.9
Which compound has the highest percentage of oxygen?
Option Compound A H2O B CO2 C NO2 D C6H12O6
Option A
Option B
Option C
Option D
Option A
Butane is a gas commonly found in lighters. Butane has a formula of C4H10. Which of the following compounds is the correct empirical formula?
Option
Formula
A
C4H10
B
CH2
C
C2H5
D
CH
Option A
Option B
Option C
Option D
Option C
What is the empirical formula composed of 79g tin and 21g O?
Sn = 79 g / 118.71 g/mol = 0.665 mol Sn /0.665 = 1
O = 21 g /15.999 g/mol = 1.31 mol O / 0.665 =1.96 = 2
Answer: SnO2
An analyst determines the percent composition of a compound to be 82.8% carbon and 17.2% hydrogen. What is the empirical formula for this compound?
C = 82.8 g / 12.011 g/mol = 6.89 mol C / 6.89 = 1 x 2 = 2
H = 17.2 g / 1.008 g/mol = 17.06 mol H / 6.89 = 2.5 x 2 = 5
Remember, when the decimal ends in 0.5, you must multiply by 2 to make that a whole number.
Answer: C2H5
What is the molecular formula for an unknown compound with an empirical formula NO2 and a molar mass of 183.99 g/mol?
Empirical formula: NO2 Mass is 46 g/mol
N = 30.4 g / 14.007 g/mol = 2.17 mol N / 2.17 = 1
O = 69.6 g / 15.999 g/mol = 4.35 mol O / 2.17 = 2
Molecular mass / Empirical Mass = 183.99 / 46 = 4
4(NO2) = N4O8
What is the molecular formula for a compound containing 92.3% carbon and 7.7% hydrogen with a molar mass of 78 g/mol?
C = 92.3 g / 12.011 g/mol = 7.68 mol C / 7.63 = 1
H = 7.7 g / 1.008 g/mol = 7.63 mol H / 7.63 = 1
Empirical formula = CH
Molar mass / Empirical mass = 78/13 = 6
Multiply the empirical formula by a factor of 6
Answer: C6H6
An 85.16 g sample of a substance contains 28.95 g of copper, 12.77 g of nitrogen and the rest of the compound is oxygen. What percent of the compound is oxygen?
C: 28.95
N: 12.77
O: 43.43
Total: 85.16
%O = 43.4385.16 = 51.00%
What is the percentage of oxygen in sulfuric acid (H2SO4)?
H: 21.0082.016
S: 132.06532.065
O: 415.99963.996
Total = 98.077
% O= 63.99698.077100= 65.3%
The most common form of rust is iron (III) oxide. The formula for rust is Fe2O3. What percent of composition of iron in rust?
- 9%
- 1%
- 7%
- 3%
69.9%
Which of the following compounds has the highest percentage of carbon?
Option Compound A C3H8 B CH4 C CO2 D C6H12O6
Option A
Option B
Option C
Option D
Option A
An unknown molecule has a molecular formula of C24H48O24. What is the empirical formula?
Option Formula A C12H24O12 B CH2O C C6H12O6 D C8H16O8
Option A
Option B
Option C
Option D
Option B
A detective finds a body at an abandoned house that appears to have died due to an overdose of pain medication. The medication in the victim’s blood contains 71.56% carbon, 6.71% hydrogen, 4.91% nitrogen, and 16.82% oxygen. Use the data below to determine which pain medication caused the victim’s death.
Pain Medication
Empirical Formula
Codeine
C18H21NO3
Acetaminophen
C8H9NO2
Morphine
C17H19NO3
Demerol
C15H21NO2
Codeine
Acetaminophen
Morphine
Demerol
Morphine
Your lab partner has finished analyzing data and asks to compare his calculations with yours. While your data was collected together, you determined the empirical formula of your compound to be C2H4O3 and your partner argues that the correct empirical formula is C6H12O9. Is your partner drawing an accurate conclusion from the data you collected?
Yes because the elements are in the same ratio.
Yes because his conclusion shows the actual number of atoms in the molecule.
No because his formula is not in simplest terms.
No because your formula only shows the ratio, not the actual number of atoms in the molecule.
No because his formula is not in simplest terms.
A compound has an empirical formula of N2O and a molecular mass of 220 g/mol. What is the molecular formula for the compound?
N: 2 x 14.007 = 28.014
O: 1 x 15.999 = 15.999
Molar Mass of Empirical Formula: 44.013
22044.013=5
Molecular Formula is N10O5.
What is the molecular formula for a compound that is composed of 44.45 g of carbon, 3.73 g of hydrogen, and 51.82 g of nitrogen and a molecular weight of 81.09 g/mol. What is its molecular formula?
C: 44.45/ 12.011 = 3.70007/ 3.6996 = 1
H: 3.73/ 1.088 = 3.75984/ 3.6996 = 1
N: 51.82/ 14.007 = 3.6996/ 3.6996 = 1
Empirical Formula: CHN, Molar mass = 27.026 g/mol
81.0927.026=3
Molecular Formula is C3H3N3
A forensic scientist determines the percent composition of a hydrocarbon to be 65% carbon, 14% hydrogen and 21% oxygen. She also determines the molar mass of the compound to be 148 g/mol. She claims the molecular formula for the compound is C8H21O2. Is this a correct conclusion that can be drawn from the data? Be sure to explain your answer.
Yes because the molecular mass and the empirical formula established by the data match. Multiplying the molar mass of the hydrocarbon by each percent and then dividing the molar mass of the individual elements, should be approximately the numbers in the given empirical formula.
What is the ratio of chlorine gas to sodium chloride according to the following reaction:
2NaF + Cl2 –> 2NaCl + F2
When looking for the ratio, look at the coefficients in the balanced chemical equation. Also, make sure you record your answer in the order in which it was asked Cl2:NaCl
Answer: 1:2
Use the following equation to answer the question: 2NaF + Cl2 –>2NaCl + F2. If Xander is working in the lab and produce 6.25 moles of fluorine gas, how many moles of sodium chloride was also produced during this reaction?
- 13 mol NaCl
- 25 mol NaCl
- 5 mol NaCl
12.5 mol NaCl
What is the mole ratio of aluminum, Al to oxygen, O2 in the following equation:
4Al + 3O2 –> 2Al2O3
When looking for the ratio, look at the coefficients in the balanced chemical equation. Also, make sure you record your answer in the order in which it was asked Al:O2
4: 3
Using the same conditions from the previous reaction:
4Al + 3O2 –> 2Al2O3
How many moles of oxygen, O2 would be needed if Luis is looking to produce 2.75 moles of aluminum oxide, Al2O3?
- 83 mol O2
- 13 mol O2
- 06 mol O2
- 67 mol O2
4.13 mol O2
Using the same conditions from the previous reaction:
4Al + 3O2 –> 2Al2O3
How many moles of aluminum, Al would be needed if Susan is looking to use all of the 13.23 moles of oxygen, O2 available in the oxygen tank in the lab?
- 98 mol Al
- 820 mol Al
- 923 mol Al
- 64 mol Al
17.64 mol Al
What unit of measure is the key to performing stoichiometric calculations?
grams
moles
molar mass
moles