The interaction of two or more drugs at the same receptor site in which one blocks the action of the other is
a. synergism.
b. antagonism.
c. cross-tolerance.
d. intolerance.

The correct option is b

Explanation:

Antagonism is caused when a chemical (in this case drug) causes the opposite effect of another chemical (in this case drug) or blocks the effect of another chemical/drug.

A commonly used example of antagonism is the opposing effects of insulin and glucagon in the body; Insulin lowers blood sugar level but glucagon raises same in the body.

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

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.