Let the mixture become water at T°C at steady state.
To convert steam at 100°C to water at T°C
Q = 1 x 540 + 1 x 1 x (100−T)
Similarly, to convert 1 g of ice to water at T°C
Q = 1 x 80 + 1 x 1 x (T − 0)
Since, both these heats should be the same,
540 + 100 − T = 80 + T
⇒ 2T = 560
⇒ T = 280°C
Since, this is not a possible value of T hence water wont exist and it will be precisely steam at 100°C