If mercury and glass had equal coefficient of volume expansion, could we make a mercury thermometer in a glass tube?

Yes, we can make. Mercury and glass have equal coefficients of volume expansion which means they have equal volumetric expansion. The coefficient of volume expansion is defined as the fractional change of volume per Kelvin rise in temperature. The accepted value of coefficient of volumetric expansion of mercury is 181 x /K. When there is a change in temperature, the increase in the volume of the glass tube would be zero. The rise in the glass tube’s volume is equal to the difference of real increase in volume and increase in the volume of the container. Hence, mercury thermometer in a glass tube will give accurate reading at every temperature.