The question is incomplete, here is a complete question.
An arctic weather balloon is filled with 27.8 L of helium gas inside a prep shed. The temperature inside the shed is 13 ⁰C. The balloon is then taken outside, where the temperature is -9 ⁰C. Calculate the new volume of the balloon. You may assume the pressure on the balloon stays constant at exactly 1 atm. Be sure your answer has the correct number of significant digits.
Answer : The new volume of the balloon is 25.7 L
Explanation :
Charles's Law : It is defined as the volume of the gas is directly proportional to the temperature of the gas at constant pressure and number of moles.

or,

where,
= initial volume of gas = 27.8 L
= final volume of gas = ?
= initial temperature of gas = 
= final temperature of gas = 
Now put all the given values in the above equation, we get:


Therefore, the new volume of the balloon is 25.7 L
H20. 2 of hydrogen and oxygen
Answer:
I dont know the answer for that question it's hard question isn't it
Answer:
Cyclopropane has a planar carbon back bone while propane does not
Explanation:
We have to recognize that in straight chain saturated organic compounds, carbon atoms have a tetrahedral geometry. Each carbon atom is bonded to four other atoms.
However, carbon atoms in cyclic compounds are also sp3 hybridized with each carbon bonded to only four other atoms but the ring system is highly strained.
Cyclopropane is a necessarily planar molecule with a bond angle that is far less than the expected tetrahedral bond angle due to strain in the molecule. Hence, the carbon atoms may have have a "planar backbone".
<span>pharmacokinetics
This question is simply a matter of knowing the definition of terms being used in your class. So let's look at the 4 options and see what makes sense.
spectrometry
* This is the determination of elements based upon the light spectrum associated with the elements. It can be either an emission spectrum you get by energizing the substance under test, or an absorption spectrum to see what wavelengths the substance absorbs. But in either case, this doesn't make sense in the statement, so it's a wrong answer.
LD50
* This terms means "Lethal Dose 50%" which is the amount of the substance needed such that half of the creatures that receive that dose die. In the context of the statement, this doesn't make sense, so it's a wrong answer.
pharmacokinetics
* This is the study of how drugs move through the body and are metabolized. This sounds like something that makes sense for the statement in the question, so it's most likely the correct answer. Let's see what the next choice is.
chromatography
* This is a laboratory method of separating substances using differential rates of diffusion. This doesn't make sense given the statement in the question, so it's a wrong choice.
So of the 4 available choices, 3 of them do not make sense given the statement in question and the only one that does make sense is "pharmacokinetics"</span>