Answer:
23892U=23490Th +42He
Explanation:
In alpha decay, the daughter nucleus is two units less than the parent in atomic number. The mass number also decreases by 4 units. The daughter is thus found two places before the parent in the periodic table.
 
        
             
        
        
        
Answer:
They all have the same number of protons but different numbers of neutrons.
Explanation:
Elements will always have the same number of protons no matter the isotopes. Isotopes only change the number of neutrons. Silicon will always have 14 protons. So silicon-28 has 14 protons and 14 neutrons. Silicon-29 has 14 protons and 15 neutrons. Silicon-30 has 14 protons and 16 neutrons.
 
        
             
        
        
        
The formula for molality---> m = moles solute/ Kg of solvent
the solute here is NH₃ because it's the one with less amount. which makes water the solvent.
1) let's convert the grams of NH₃ to moles using the molar mass
molar mass of NH₃= 14.0 + (3 x 1.01)= 17.03 g/ mol
15.0 g (1 mol/ 17.03 g)= 0.881 mol NH₃
2) let's convert the grams of water into kilograms (just divide by 1000)
250.0 g= 0.2500 kg
3) let's plug in the values into the molality formula
molality= mol/ Kg---> 0.881 mol/ 0.2500 kg= 3.52 m
        
             
        
        
        
Answer:
a)
b)
Explanation:
a) The reaction: 

The free-energy expression:

![E=E_{red}-E_{ox]](https://tex.z-dn.net/?f=E%3DE_%7Bred%7D-E_%7Box%5D)
The element wich is reduced is the Fe and the one that oxidates is the Mg: 

The electrons transfered (n) in this reaction are 2, so: 


b) If you have values of enthalpy and enthropy you can calculate the free-energy by: 

with T in Kelvin

