4) A 4.00 L balloon is filled with 0.297 moles of helium gas with a pressure of

149

Explanation:

Using the ideal gas equation; PV = nRT

P= Pressure = 0.910 atm,     T= Temperature = ?

V= Volume = 4.0L                  R = Gas constant = 0.08206 L.atm/mol/K

n = number of moles = 0.297

Making 'T' the subject of the formular, we have;

T = P V/ n R   =  0.910  x 4  /  0.297 x 0.08206

                       =  149

A ) 1, 2 and 3

Explanation:

1 ) is correct because,

K donates 1 electron

F gain 1 electron from K.

If donating and gaining of electrons takes place between two electron, then type of compound formed is ionic.

2 ) is correct because,

K + F > KF

3 ) is correct because,

KF is soluble in cold water; very soluble in hot water.