An ideal monoatomic gas is kept in a rigid container that expands negligibly when heated. The gas starts at a temperature of 17.0 deg C, and heat is added to increase its temperature. At what temperature will its root-mean-square speed (thermal speed) be 1.2 times its value at 17.0 deg C (20 % increase)

145 ° C

Explanation:

Using the expression

where T = 17 ° C = (273 + 17) K

                            = 290 K

So; At what temperature will its root-mean-square speed (thermal speed) be 1.2 times its value at 17.0 deg C?

What this implies is that:

      where R & M are constant

T = 144.6  ° C

T = 145  ° C

not moving. pos accel,