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Post-Laboratory Questions (use the spaces provided for the answers and additiona

ID: 504422 • Letter: P

Question

Post-Laboratory Questions (use the spaces provided for the answers and additional paper ifnecessary. 1. A student was given only one graduated cylinder to use for this experiment. After using it to measure 50.0 of the assigned acid, the student failed to rinse or dry the cylinder before out the 50.5 mL of the base. Would the calculated AH be higher, lower, or the same as the literature 4Hneuten? Briefly explain this difference as a result of using only one graduated cylinder for the experiment. 2. Explain how the following changes in the procedure for this experiment would affect the results. a) A glass beaker was used instead of a pressed polystyrene cup. (2) A pressed polystyrene top was used to cover the polystyrene cup after the acid and base solutions had been mixed.

Explanation / Answer

Q1.

V = 50 mL acid

V = 50.5 mL of base

what happens to dHrxn,

it will NOT be modified, since the mmol of acid will be limiting the reaction, so the extra base does not afftect the reaction.

The HRxn neutralization will be pretty similar to the value of 50.0 mL of base

Q2.

Glass will not maintain the temperature as a polystyrene cup

It has --> no adiabatic features

so dT = small tha real

Then, the Heat calculated is lower for that reaction

HRxn will be lower

Q2.

Not much effect, since the top is small, the air is not good conductor of heat, so it is not lost htat rapidly as in th eprevious example

the HRxn remains similar

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