The tribute states of the ancient Aztec empire
were governed directly by the emperor.
made regular payments to the emperor.
acted as powerful independent city-states.
O surrounded the main Aztec city-state.

made regular payments to the emperor.

Explanation:

The Aztec Empire was an alliance of three states: Mexico-Tenochtitlan, Texcoco, and Tlacopan. The area in and around the Valley of Mexico was ruled by these three city-states from 1428 to 1521. The state religion of the empire was polytheistic. The tribute states of the ancient Aztec empire made regular payments to the emperor.

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol