There are 4 ways the sum of the dice is 5: 1+4, 4+1 and 2+3 and 3+2, out of 36 possible outcomes.
There are only two ways the sum of the dice is 11: 5+6 and 6+5.
(i) The probabilities are different but one event cannot be said to cause the other. In that sense they are independent.
(ii) The probability of the sum of 5 is 4/36=1/9. The probability of the sum of 11 is 2/36=1/18.