Examine each of these chemical equations to determine which equation is correctly balanced.

Options: i. Mg(NO_{3})_{2} + K_{2}CO_{3} -> MgCO_{3} + KNO_{3}. ii. Mg(NO_{3})_{2} + K_{2}CO_{3} -> MgCO_{3} + 2KNO_{3}. iii. 2Mg(NO_{3})_{2} + K_{2}CO_{3} -> 2MgCO_{3} + KNO_{3}. iv. Mg(NO_{3})_{2} + 2K_{2}CO_{3} -> MgCO_{3} + 2KNO_{3}.
ii.