Chem 121 Exam 1 Certification Evaluation Tested Questions Full Solution Guide

CHEM 121 EXAM 1 CERTIFICATION EVALUATION TESTED QUESTIONS FULL SOLUTION
GUIDE
CHEM 121 EXAM 1 Questions and Answers Verified
Solutions Latest Update 2026/2027

Question:
How many moles of carbon would be found in 52.4 g C3H8

Answer:
b. First calculate how many moles of C3H8 there are (1.19 moles). Then multiply by molar ratio (3
mol C/1 mol propane) = 3.57 mol C



Question:
Which of the following is a postulate of Dalton's atomic theory? a. Atoms combine in whole number
ratios to form compounds b. Atoms contain a tiny dense nucleus c. Protons are found in the nucleus
of an atom d. The number of neutrons in an atom determines the identity of the element e. Atoms
contain electrons.

Answer:
a. Atoms combine in whole number ratios to form compounds



Question:
The density of an unknown substance is 8.76 g/cm3. How many cm3 would a 98.3 g sample of this
substance occupy?

Answer:
c. multiply 98.3 g by (1 cm3/8.76 g) to make 11.2 g/cm3



Question:
Which of the following statements is TRUE about these 3 atoms: 43/23 V (this means Vanadium
with a 43 on upper left and 23 on lower left); 40/20 Ca^2+; 37/17 Cl^- a. All of the atoms are
isotopes of one another b. All of the atoms have the same number of electrons c. All of the atoms
have the same number of protons d. All of the atoms have the same number of neutrons e. All of the
atoms belong in the fourth period

,Answer:
d. all of the atoms have the same number of neutrons



Question:
How many significant figures are present in the following calculations (SHOW WORK) (2 pts)
(24.3 - 15.44) / 3.242

Answer:
=8.9/3.242 = 2.7. Two sig figures. The subtraction part gives one decimal place after the decimal,
because that was the level of uncertainty in the subtraction. That number thus as 2 sig digits.



Question:
4 NH3 + 7 O2 --> 4 NO2 + 6 H2O If 5.82 moles of NH3 are reacted with 9.74 moles of oxygen gas,
how many moles of NO2 will be formed? Which reactant is limiting? (3 pts)

Answer:
5.82 mol NH3 ( 4 mol NO2/4 mol NH3) = 5.82; 9.74 mol O2 (4/7) = 5.57 mol NO2 so O2 is
limiting and can only make 5.57 moles of NO2



Question:
Balance, including the states of matter: The reaction of solid aluminum with liquid bromine to form
solid aluminum bromide (1 pts)

Answer:
2 Al (s) + 3 Br2 (l) --> 2 AlBr3 (g)



Question:
Balance, including the states of matter: Al(ClO4)3 (aq) + Ba(OH)2 (aq) --> Ba(ClO4)2 (aq) +
Al(OH)3 (g)

Answer:
3 Al(ClO4)3 (aq) + 3 Ba(OH)2 (aq) --> 3 Ba(ClO4)2 (aq) + 2 AL(OH)3 (s)

, Question:
Balance, including the states of matter: The combustion of C5 H10 O in oxygen gas to corm carbon
dioxide gas and water vapor

Answer:
C5H10O + 7O2 --> 5 CO2 (g) + 5 H2O (g)



Question:
Give an example of each of the following: (.5 pts each) a. Alkaline earth metal b. noble gas c.
transition metal d. metalloid

Answer:
Ca, Ar, Fe, Si Why does the mass of an element in the periodic table not have whole numbers (2 pts)



Question:


Answer:
The mass in the periodic table is a weighted average of all isotopes of bromine. So no atom has a
mass of 79.9 amu, but the average of all the isotopes, weighted by their abundance is 79.9 amu.



Question:
Identify the type of the compound, name it, write the correct formula, and say if it is ionic or
molecular: trisulfur hexafluoride (1 pt)

Answer:
S3F6, molecular



Question:
Identify the type of the compound, name it, write the correct formula, and say if it is ionic or
molecular: Ba(MnO4)2