Acatalyst is

the product of a combustion reaction

a solid product of a reaction

not used up in a reaction

one of the reactants in a single-replacement reaction

The definition of a catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Explanation:

I googled it :D

coral.

explanation:

coral. many marine organisms that produce calcium carbonate shells or skeletons are negatively impacted by increasing co2 levels and decreasing ph in seawater.

explanation:

venn diagram is pictorial representation with of circles showing the relation between two finite sets or things. the intersection part of two circles conveys the relation present in between those sets or things.

here in the venn diagram of sand and salt two circles represent sand and salt. but the area falling under the intersection of these circle represents the mixture of sand and salt.

so, in a venn diagram the mixture will be placed in a middle that is in between the intersection of two circles.