Horizon International School
C C
hemistry
ompetition
Answer key
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Answer
Question
Answer
Name:_________________Grade 10
1
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
1. Each of the four types of reaction stoichiometry problems requires using a
a. table of bond energies.
c. Lewis structure.
b. chart of electron configurations.
d. mole ratio.
____
2. Which equation is not balanced?
a.
b.
c.
d.
____
3. Which coefficients correctly balance the formula
a. 1,2,2
c. 2,1,1
b. 1,1,2
d. 2,2,2
____
4. When the formula equation
a. 3.
b. 2.
____
?
is correctly balanced the coefficient of Fe is number
c. 7.
d. 9.
5. Given the equation
, the starting mass of A, and its molar mass, and you are asked to
determine the moles of C produced, your first step in solving the problem is the multiply the given mass of A
by
a.
c.
b.
d.
____
6. In the chemical reaction represented by the equation wA + xB  yC + zD, a comparison of the number of
moles of A to the number of moles of C would be a(n)
a. mass ratio.
c. electron ratio.
b. mole ratio.
d. energy proportion.
____
7. In the chemical equation wA + xB  yC + zD, if one knows the mass of A and the molar masses of A, B, C,
and D, one can determine
a. the mass of any of the reactants or products.
b. the mass of B only.
c. the total mass of C and D only.
d. the total mass of A and B only.
____
8. The units of molar mass are
a. g/mol.
b. mol/g.
____
c. amu/mol.
d. amu/g.
9. If one knows the mass and molar mass of reactant A and the molar mass of product D in a chemical reaction,
one can determine the mass of product D produced by using the
a. mole ratio of D to A from the chemical equation.
b. group numbers of the elements of A and D in the periodic table.
c. estimated bond energies involved in the reaction.
d. electron configurations of the atoms in A and D.
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____ 10. In the reaction represented by the equation N2 + 3H2  2NH3, what is the mole ratio of nitrogen to ammonia?
a. 1:1
c. 1:3
b. 1:2
d. 2:3
____ 11. In the reaction represented by the equation 2Al2O3  4Al + 3O2, what is the mole ratio of aluminum to
oxygen?
a. 10:6
c. 2:3
b. 3:4
d. 4:3
____ 12. In the reaction represented by the equation C + 2H2  CH4, what is the mole ratio of hydrogen to methane?
a. 1:1
c. 1:2
b. 2:1
d. 2:4
____ 13. In the reaction represented by the equation N2 + 3H2  2NH3, what is the mole ratio of hydrogen to
ammonia?
a. 1:1
c. 3:2
b. 2:1
d. 6:8
____ 14. The Haber process for producing ammonia commercially is represented by the equation N2(g) + 3H2(g) 
2NH3(g). To completely convert 9.0 mol hydrogen gas to ammonia gas, how many moles of nitrogen gas are
required?
a. 1.0 mol
c. 3.0 mol
b. 2.0 mol
d. 6.0 mol
____ 15. In the equation 2KClO3  2KCl + 3O2, how many moles of oxygen are produced when 3.0 mol of KClO3
decompose completely?
a. 1.0 mol
c. 3.0 mol
b. 2.5 mol
d. 4.5 mol
____ 16. What is the Molarity of a 100. mL aqueous solution that contains 1.00 g KCl (molar mass = 74.55 g/mol)?
a. 1.34 M KCl
b. 0.134 M KCl
c. 0.0134 M KCl
d. 0.001 34 M KCl
____ 17. To determine the molarity of an HCl solution, you need to know the number of
a. grams of HCl in 1 106 g of solution.
b. moles of HCl dissolved in the total moles of solution.
c. moles of HCl in 1 L of solution.
d. moles of HCl dissolved in 1 kg of solvent.
____ 18. What type of solute-solvent combination is carbon dioxide in water?
a. gas-liquid
b. liquid-gas
c. liquid-liquid
d. cannot be determined
____ 19. What is the molarity of a solution that contains 0.202 mol KCl (molar mass = 74.55 g/mol) in 7.98 L of
solution?
a. 0.0132 M KCl
b. 0.0253 M KCl
c. 0.459 M KCl
d. 1.36 M KCl
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____ 20. What is the molarity of a solution that contains 125 g NaCl (molar mass = 58.44 g/mol) in 4.00 L solution?
a. 0.535 M NaCl
b. 2.14 M NaCl
c. 8.56 M NaCl
d. 31.3 M NaCl
____ 21. How many moles of HCl (molar mass = 36.46 g/mol) are present in 0.70 L of a 0.33 M HCl solution?
a. 0.23 mol
b. 0.28 mol
c. 0.38 mol
d. 0.47 mol
____ 22. A NaOH solution contains 1.90 mol of NaOH (molar mass = 40.00 g/mol), and its Molarity is 0.555 M. What
is its volume?
a. 0.623 L
b. 0.911 L
c. 1.05 L
d. 3.42 L
____ 23. Which type of mixture contains the smallest particles?
a. emulsions
b. solutions
c. suspensions
d. colloids
____ 24. What is the molality of an aqueous NaOH solution made with 5.00 kg of water and 3.6 mol NaOH (molar
mass = 40.00 g/mol)?
a. 3.6 m NaOH
b. 1.4 m NaOH
c. 0.72 m NaOH
d. 0.090 m NaOH
____ 25. How much methanol, CH3OH (molar mass = 32.05 g/mol), is needed to make a 0.90 m solution in 250 g of
water?
a. 0.14 g CH3OH
b. 7.2 g CH3OH
c. 100 g CH3OH
d. 220 g CH3OH
____ 26. What mass of NaCl (molar mass = 58.44 g/mol) is needed to make a 1.50 m solution using 300. g of solvent?
a. 26.3 g NaCl
b. 11.7 g NaCl
c. 1.50 g NaCl
d. 0.0877 g NaCl
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____ 27. Which mixture can be separated by filtration?
a. mayonnaise
b. muddy water
c. shaving cream
d. gelatin
____ 28. Which is an example of a solid-liquid solution?
a. alcohol-water solution
b. oxygen-nitrogen solution
c. sugar-water solution
d. copper-nickel solution
____ 29. To conduct electricity, a solution must contain
a. nonpolar molecules.
b. polar molecules.
c. ions.
d. free electrons.
____ 30. The units of Molarity is
a. M.
b. mol/L.
c. amu/mol.
d. a and b.
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