Two protons that are very far apart are hurled straight at each other, each with an initial kinetic energy of 0.19 mev, where 1 mega electron volt is equal to 1multiply106 multiply (1.6multiply10-19) joules. what is the separation of the protons from each other when they momentarily come to a stop?

When the potential energy of the electric force would be equal to the initial kinetic energy it will come to a break. The electric potential energy is denoted as q1*q2 / 4π*e0*x, while the kinetic energy is 2*0.17MeV. 
1 eV = 1.6*10^-19 J
The energy at distance x is equal to (qe^2 / 4π*e0) / x = 1.438*10^-9 eV*m / x 
x = 1.438*10^-9 / 0.34*10^6 
x = 4.229*10^-15 m