Activity B.3 Relationships in Acid-Base Reactions
Lab Report
Collective Analysis
A variable is a property of an object that can take on different values. The relationships between
four variables were explored in experiments A (Part I) and B (Part II). The variables were VHCl
(volume of hydrochloric acid), NNaOH (total number of drops of sodium hydroxide) and VH2O
(volume of water), and T (temperature change). Variables can be categorized into different
classes; this provides a structure to the data set that can help you to identify patterns (i.e.,
relationships between the values of two or more variables). In the sciences, experiments are
designed to explore relationships between independent and dependent variables.
1. Identify the independent variable and dependent variable in Experiment A.
Type of Variable Variable Name Experiment A
Independent Variable Volume of HCl
Dependent Variable Number of NaOH drops
1a) Briefly explain the reasons why you identified the variables above as independent or
dependent.
The volume of HCl is the variable that is being manipulated to observe the amount of NaoH
required to neutralize the solution, therefore the volume of HCl, the independent variable,
determines the amount of NaOH drops, the dependent variable, required to balance pH
1b) Describe the relationship between the independent and dependent variable in Experiment A.
The independent variable, volume of HCl, determines the amount of NaOH drops, the
dependent variable, required to neutralize the solution
1c). Consider experiment A in which the variable VH2O changed values between test tubes
containing the same VHCl (e.g., between test tubes A1 and A2). Was the relationship between the
two variables VHCl and NNaOH affected by the variable VH2O? Support your reasoning using data
from the group file as evidence. [Hint: you may want to calculate average values of the
dependent variable for each value of VH2O]
The variable VH2O had no effect on the relationship between the two variables VHCl and NNaOH.
The ratio between VHCl and NNaOH remained constant. While some variation did occur, it was
statistically nonsignificant
, 2. Identify the independent variable and dependent variable in experiment B. Describe the
relationship between these two variables.
Type of Variable Variable Name Experiment B
Independent Variable Volume of NaOH
Dependent Variable Solution Temperature
2a) Briefly explain the reasons why you identified the variables above as independent or
dependent.
The volume of NaOH is the variable that is being manipulated to observe the change in
temperature of the solution, therefore the volume of NaOH, the independent variable,
determines the temperature, the dependent variable, of the solution.
2b) Describe the relationship between the independent and dependent variable in Experiment B.
The independent variable, volume of NaOH, determines the temperature, the dependent
variable, of the solution
2c) Consider Experiment B in which the variable V H2O changed values between test tubes having
the same VNaOH (e.g, between test tubes B3 and B4). Was the relationship between the two
variables NNaOH and T affected by the variable VH2O? Support your reasoning using data from
the group file as evidence. [Hint: you may want to calculate average values of the dependent
variable for each value of VH2O]
The variable VH2O had an effect on the relationship between the two variables VNaOH and T. As
VH2O increased, the difference in initial and final temperature of the solution increased. In B3
VH2O is 1.0mL and the average difference in temperature is 3.6 C. In B5 VH2O is 3.4mL and the
average difference in temperature is 5.5 C.
3. Two chemical systems, interaction between hydrochloric acid and sodium hydroxide and the
interaction between hydrochloric acid and potassium hydroxide, were investigated. Use the
collection of data from the group file to plot volume of base (y-axis) versus volume of
hydrochloric acid (x-axis) data from both systems. Use different markers to identify the
different systems.
2
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