If you need half the volume, you need double the pressure (V * p). Normal air pressure in the atmosphere is 101300 Pa so that means you need double that, thus 202600 Pa (or 2,026 bars)
Answer:

Explanation:
Hello,
In this case, the first step is to compute the difference in the electronegativity for the formed bond between gallium and phosphorous by:

Thus, we can compute the percentage of ionic character by:

So the fraction is just:

Which has sense since gallium phosphide is a non-polar compound.
Regards.