Select all that apply. which of the following are homogeneous solutions? salt water air sand and water vinegar cement

salt water, air and vinegar are homogeneous solutions.

Explanation:

A solution which consists of particles of same proportion is known as a homogeneous solution. Whereas a solution which consists of particles of different proportion is known as a heterogeneous solution.

Salt and water are homogeneous solutions as salt completely disperses in water and forms a clear solution as the particles of salt and water are in proportion.

Air is composed of different gases like nitrogen, oxygen etc are all mixed in fixed ratio. Therefore, air is a homogeneous mixture.

Sand and water are heterogeneous solution as the ration of mixing is different and more over sand particles can be separated from water. Thus, it is not a homogeneous mixture.

Vinegar is also a homogeneous solution as it is composed of acetic acid and water which are mixed in fixed proportion.

Cement is a heterogeneous mixture as it is composed of a number of different substances mixed in different proportions.

Thus, we can conclude that salt water, air and vinegar are homogeneous solutions.

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.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.