原帖由 johnson 於 2014-4-22 15:00 發表
Q9 : A
- burette : rinse with titrant + water
- pipette : rinse with titrand + water
- conical flask : only rise with water
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Q9:A
burette&pipette rinse with water to remove impurites, rinse with titrant to ensure the concentration of the titrant unchange
conical flask should rinse with water only, add titrant will affect the result as more titrant instead of 25cm^3 is used
Q10:C
Q11:A
3 may be correct as its central atom bond with 3 other atom & a lone pair electrons.
If you say more specific, 3 is incorrect as it is trigonal pyramidal.
Q?:A
as 25cm^3 of NaOH is used to neutralize HCl
NaOH+HCl→NaCl+H2O
the volume of NaOH=Volume of HCl
It is a complete neutralization, temperature rise without drop
therefore, the final reading must not be straight
Actually, it is hard to tell you the answer as temperature rise, cooler NaOH is added. Although heat is generate, as the volume(mass) of the solution change, the temperature is really hard to tell.
However, if you calculate on each 2.5 cm^3 with known value of standard enthaply change of neutralization of NaOH&HCl , you will found that volume increase won't lead to a temperature drop.
Thus, A is the answer if neglect heat lost to the surroundings.