Midterm Exam Flashcards
If the density of an unknown gas Z is 4.50 g/L at STP, what is the molar mass of gas Z? Answer has to be in correct number of significant figures. No units just number.
?
A student measured the temperature of a boiling solution and found it to be 4.5°C at standard pressure. The theoretical temperature of that boiling solution is 5.5°C. What is the percent of error in the student’s measurement?
?
How many significant digits are in 0.034510?
Five
The empirical formula for a compound is CH2O, and the molar mass is 180.2 g/mol. Which is the molecular formula for this compound?
C6H12O6
What is the number of moles in 432 g Ba(NO3)2? Answer must be in correct number of significant figures.
?
How many protons are in an atom represented by 22088Ra?
88
Sulfur forms a 2– ion. How many electrons does a sulfide ion have?
18
Which is the correct formula for iron (III) sulfate?
Fe2 (SO4)3
There is element “X” that exists as two naturally occurring isotopes. X-35 occurs 75% of the time and X-37 occurs 25% of the time. Calculate the average atomic mass of element X?
35.5
According to the periodic table, which of the following series of elements is ordered according to decreasing reactivity?
Cs, Mg, Si, He
In HNO3, the oxidation state of hydrogen is +1 and the oxidation state of oxygen is -2. Therefore, the oxidation state of nitrogen is
+5
The mass of an object was recorded as 19.93 g, 19.90 g, and 20.02 g, using an electronic analytical balance. What is the average of these three masses expressed to the correct number of significant figures?
19.95
If 60.2 grams of Hg combines completely with 24.0 grams of Br to form a compound, what is the percent composition of Hg in the compound? Answer must be in corrent number of significant figures. Do not type % sign, just number.
71.5
An increase in atomic number is related to an increase in atomic mass because
an increase in proton in the nucleus
What determines the chemical properties of an element?
The number of valence electrons
