The equation below shows the reaction of zinc with hydrochloric acid (hcl).
zn (s) + 2 hcl (aq) —> zncl2 (aq) + h2 (g)
what will happen if the concentration of hcl is decreased?
a. more zncl2 will be produced.
b. the reaction rate will slow down.
c. the hydrochloric acid will become more acidic.
d. the reaction will produce water instead of hydrogen gas.

B. The reaction rate will slow down.

Explanation:

As concentration increases, rate of the reaction will increase. When there are more particles present in a system, more collision will take place.

As collision increases, rate of the reaction will increase. Concentration makes the molecules to come closer together thus leading to more collisions.

Rate of the reaction is directly proportional to the reactant collisions.

Orientation of the molecule and molecule possessing enough energy  will lead to increased number of collisions thereby increasing the rate of the reaction .

So, Increasing the concentration of a reactant increases the frequency of collisions between reactants and will, therefore, increase the reaction rate

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