CHEM 126 LAB FINAL EXAM QUESTIONS AND ACCURATE
ANSWERS A+ GRADED
The accuracy of a single measurement can be determined by comparison to a "known value."
What additional information, if any, is needed in order to state the precision of the
measurement? - ANSWER multiple data points are needed to determine precision
A primitive cubic unit cell has how many atoms? - ANSWER 1 atom
A primitive cubic unit cell has what coordination number? - ANSWER 6
A primitive cubic unit cell has what percent occupied volume? - ANSWER the least
In a primitive cubic unit cell where do the atoms touch? - ANSWER along the edge length
What is the formula for a primitive cubic unit cell? - ANSWER 2r=l
A face centered cubic unit cell has how many atoms? - ANSWER 4 atoms
A face centered cubic unit cell has what coordination number? - ANSWER 12
A face centered cubic unit cell has what percent occupied volume? - ANSWER the most
,In a face centered cubic unit cell, where do the atoms touch? - ANSWER along the face
diagonal
What is the formula for a face centered cubic unit cell? - ANSWER 4r=l√2
A body centered cubic unit cell has how many atoms? - ANSWER 2 atoms
A body centered cubic unit cell has what coordination number? - ANSWER 8
A body centered cubic unit cell has what percent occupied volume? - ANSWER the middle
In a body centered cubic unit cell where do the atoms touch? - ANSWER along the body
diagonal
What is the equation in a body centered cubic unit cell? - ANSWER 4r=l√3
When plotting on a graph to get a straight line, what information can be derived from the
graph? - ANSWER slope, y intercept
What plotting "temperature" vs. "pressure" which is on the y axis - ANSWER temperature
, How would a determination of the boiling point elevation constant be affected by forgetting
to account for the fact that the compound is ionic and breaks up into 3 ions per formula unit?
- ANSWER the boiling point is measure and the concentration in molality is known. the kb is
calculated from the equation ∆tb= ikbm, the true value of kb should be a third of the value of
the calculated kb if the value of i is not used
What are some sources of error possible in the colligative properties experiment? - ANSWER
unknowingly losing mass of solute, measure boiling point is smaller, calculated molality is
smaller, calculated moles is smaller and thus molar mass is larger
Do you know what to graph in order to determine the order of a reaction with respect to one
substance whose concentration is changing? - ANSWER so that one can determine whether it
is zero, first or second order in the following make a graph of [A] vs. time, ln[A] vs. time and
1/[A] vs. time to identity the order
How would you drive a reaction that is endothermic and has a greater number of gaseous
reactant than gaseous products? - ANSWER heat it and increase the pressure
Explain how an increase in temperature affects the equilibrium of an exothermic reaction and
explain the effect on the equilibrium constant - ANSWER heating an exothermic reaction will
cause it to reach equilibrium by making more reactants and the increase in temperature
causes the equilibrium constant to decrease
Why is it possible to separate Cu2+ from Mg2+ using NH3? - ANSWER both the Cu2+ and
Mg2+ react with OH- that is present in producing the blue precipitate with the Cu2+
ANSWERS A+ GRADED
The accuracy of a single measurement can be determined by comparison to a "known value."
What additional information, if any, is needed in order to state the precision of the
measurement? - ANSWER multiple data points are needed to determine precision
A primitive cubic unit cell has how many atoms? - ANSWER 1 atom
A primitive cubic unit cell has what coordination number? - ANSWER 6
A primitive cubic unit cell has what percent occupied volume? - ANSWER the least
In a primitive cubic unit cell where do the atoms touch? - ANSWER along the edge length
What is the formula for a primitive cubic unit cell? - ANSWER 2r=l
A face centered cubic unit cell has how many atoms? - ANSWER 4 atoms
A face centered cubic unit cell has what coordination number? - ANSWER 12
A face centered cubic unit cell has what percent occupied volume? - ANSWER the most
,In a face centered cubic unit cell, where do the atoms touch? - ANSWER along the face
diagonal
What is the formula for a face centered cubic unit cell? - ANSWER 4r=l√2
A body centered cubic unit cell has how many atoms? - ANSWER 2 atoms
A body centered cubic unit cell has what coordination number? - ANSWER 8
A body centered cubic unit cell has what percent occupied volume? - ANSWER the middle
In a body centered cubic unit cell where do the atoms touch? - ANSWER along the body
diagonal
What is the equation in a body centered cubic unit cell? - ANSWER 4r=l√3
When plotting on a graph to get a straight line, what information can be derived from the
graph? - ANSWER slope, y intercept
What plotting "temperature" vs. "pressure" which is on the y axis - ANSWER temperature
, How would a determination of the boiling point elevation constant be affected by forgetting
to account for the fact that the compound is ionic and breaks up into 3 ions per formula unit?
- ANSWER the boiling point is measure and the concentration in molality is known. the kb is
calculated from the equation ∆tb= ikbm, the true value of kb should be a third of the value of
the calculated kb if the value of i is not used
What are some sources of error possible in the colligative properties experiment? - ANSWER
unknowingly losing mass of solute, measure boiling point is smaller, calculated molality is
smaller, calculated moles is smaller and thus molar mass is larger
Do you know what to graph in order to determine the order of a reaction with respect to one
substance whose concentration is changing? - ANSWER so that one can determine whether it
is zero, first or second order in the following make a graph of [A] vs. time, ln[A] vs. time and
1/[A] vs. time to identity the order
How would you drive a reaction that is endothermic and has a greater number of gaseous
reactant than gaseous products? - ANSWER heat it and increase the pressure
Explain how an increase in temperature affects the equilibrium of an exothermic reaction and
explain the effect on the equilibrium constant - ANSWER heating an exothermic reaction will
cause it to reach equilibrium by making more reactants and the increase in temperature
causes the equilibrium constant to decrease
Why is it possible to separate Cu2+ from Mg2+ using NH3? - ANSWER both the Cu2+ and
Mg2+ react with OH- that is present in producing the blue precipitate with the Cu2+
