Astudent dissolves 20.0 g of glucose into 511 ml of water at 25 c the vapor pressure of pure water at 25 c is 3.13

3.12 × 10⁻² atm

Explanation:

A student dissolves 20.0 g of glucose into 511 mL of water. At 25 °C, the vapor pressure of pure water at 25 C is 3.13 × 10⁻² atm. I think the question is: "What is the vapor pressure of the solution?"

According to Raoult's law, the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent times the mole fraction of the solvent present.

The molar mass of glucose is 180.16 g/mol. The moles corresponding to 20.0 g of glucose are:

20.0 g × (1 mol/180.16 g) = 0.111 mol

The density of water at 25°C is 0.997 g/mL. The mass corresponding to 511 mL of water is:

511 mL × (0.997 g/mL) = 509 g

The molar mass of water is 18.02 g/mol. The moles corresponding to 509 g of water are:

509 g × (1 mol/18.02 g) = 28.2 mol

The total number of moles is 0.111 mol + 28.2 mol = 28.3 mol

The mole fraction of water is:

The vapor pressure of a solvent above the solution is:

send me question so i can u

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.