Answer: D
Explanation: I got it wrong on my test :( and got this answer as correct.
Answer:

Explanation:
Hello there!
In this case, according to the given STP (standard pressure and temperature), it is possible for us to realize that the equation to use here is the Avogadro's law as a directly proportional relationship between moles and volume:

In such a way, given the initial volume and both initial and final moles, we can easily compute the final volume as shown below:

Best regards!
The total atomic number must be the same on each side. The total mass number must be the same on both side.
<span>On the RHS, for the mass number, we have 257 + 4 = 261 (the 4 comes from the 4 neutrons). That means the mass number of the missing piece on the LHS is 261 - 247 = 14. </span>
<span>One the RHS, for the atomic number we have a total of 104 since the 4 neutrons are all neutral. On the LHS, we have this: 104 - 98 = 6. </span>
<span>The missing piece is a nucleus of carbon 14. Done in your style, it is 14/6C</span>