A eudiometer is used to collect hydrogen gas in a chemical reaction, as in your Exp 7. The volume of the gas in the tube (when pressure is held constant) is 479.10 mL. The pressure of the atmosphere during the experiment is 758.3 mmgHg, and the temperature of the water and gas is
19.0*C. The water vapor pressure at this temperature is 16.5 torr.
Calculate the mass of hydrogen, in mg, collected.

39.29 mg

Explanation:

Step 1: Calculate the partial pressure of hydrogen

The pressure of the atmosphere is equal to the sum of the partial pressures of the water and the hydrogen. (1 Torr = 1 mmHg)

P = pH₂O + pH₂

pH₂ = P - pH₂O = 758.3 mmHg - 16.5 mmHg = 741.8 mmHg

We will convert it using the conversion factor 1 atm = 760.0 mmHg.

741.8 mmHg × 1 atm/760.0 mmHg = 0.9761 atm

Step 2: Convert 19.0 °C to Kelvin

We will use the following expression.

K = °C + 273.15 = 19.0 + 273.15 = 292.2 K

Step 3: Calculate the mass of hydrogen

First, we will calculate the moles of hydrogen using the ideal gas equation.

P × V = n × R × T

n = P × V / R × T

n = 0.9761 atm × 0.47910 L / (0.08206 atm.L/mol.K) × 292.2 K = 0.01950 mol

The molar mass of hydrogen is 2.015 g/mol. The mass of hydrogen is:

0.01950 mol × 2.015 g/mol = 0.03929 g = 39.29 mg

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.

2b2t

explanation:

2b2t