Answer:
Part A:
to two significant figures
Part B:
to two significant figures
Part C:
to two significant figures
Explanation:
Given that :
mass of the hydrogen = 0.30 g
the molar mass of hydrogen gas molecule = 2 g/mol
we all know that:
number of moles = mass/molar mass
number of moles = 0.30 g /2 g/mol
number of moles = 0.15 mol
For low temperature between the range of 50 K to 100 K, the specific heat at constant volume for a diatomic gas molecule = 
For Part A:




to two significant figures
Part B. For hot temperature, 




to two significant figures
Part C. For an extremely hot temperature, 




to two significant figures
General Characteristics of Acids & Bases. Chemists measure the strength of an acid or base by its pH, which is a term that refers to the "power of hydrogen.". The midpoint of the pH scale is neutral. Compounds with a pH lower than the midpoint value are acidic while those with a higher value are basic or alkaline.
The available options are: (found the complete text on internet)
A- at a distance less than r
B- at a distance equal to r
C- at a distance greater than r
Solution:
The correct answer is C) at a distance greater than r.
In fact, the gravitational attraction between the satellite and the Earth provides the centripetal force that keeps the satellite in circular orbit, so we can write

where the term on the left is the gravitational force, while the term on the right is the centripetal force, and where
G is the gravitational constant
M is the Earth mass
m is the satellite mass
r is the distance of the satellite from the Earth's center
v is the satellite speed
Re-arranging the equation, we get

and we see from this formula that, if the second satellite has a speed less than the speed v of the first satellite, it means that the denominator of the fraction is smaller, and so r is larger for the second satellite.
Let the mass of 2500 kg car be
and it's velocity be
and the mass of 1500 kg car be
and it's velocity be
.
After the bumping the mass be M and it's velocity be V.
By law of conservation of momentum we have

2500 * 5 + 1500 * 1=4000 * V
V = 14000/4000 = 7/2 = 3.5 m/s
So the velocity of the two-car train = 3.5 m/s
Note: I'm not sure what do you mean by "weight 0.05 kg/L". I assume it means the mass per unit of length, so it should be "0.05 kg/m".
Solution:
The fundamental frequency in a standing wave is given by

where L is the length of the string, T the tension and m its mass. If we plug the data of the problem into the equation, we find

The wavelength of the standing wave is instead twice the length of the string:

So the speed of the wave is

And the time the pulse takes to reach the shop is the distance covered divided by the speed: