An aqueous solution of hydroiodic acid is standardized by titration with a 0.168 M solution of sodium hydroxide. If 18.7 mL of base are required to neutralize 29.6 mL of the acid, what is the molarity of the hydroiodic acid solution

0.106M

Explanation:

Equation of reaction

NaOH + HI ===》 NaI + H₂O

If 0.168 moles of NaOH = 1000cm³

X moles = 18.7 cm³

X = (18.7 * 0.168) / 1000 = 0.00314 moles

From equation of reaction,

1 moles of NaOH = 1 mole of HI

0.00314 moles of NaOH = 0.00314 moles of HI

Therefore,

0.00314 moles of HI = 29.6cm³

X moles = 1000cm³

X = (0.00314 * 1000) / 29.6 = 0.106M

chemical energy is stored in the chemical bonds of atoms and molecules. it can only be seen when it is released in a chemical reaction. when chemical energy is released, the substance from which the energy came is often changed into an entirely different substance.

this chemical reaction releases energy in the form of light and heat. chemical energy is the potential energy stored in the arrangement of atoms within molecules. breaking chemical bonds requires energy, while forming new chemical bonds releases energy.

the atp molecule can store energy in the form of a high energy phosphate bond joining the terminal phosphate group to the rest of the molecule. in this form,energy can be stored at one location, then moved from one part of the cell to another, where it can be released to drive other biochemical reactions.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.