13.
balance the equation.
ca(no3)2 + na2co, → caco3 + na no3

Ca(NO3)2 + Na2CO3 -> CaCO3 + 2NaNO3

Explanation:

As Calcium ion (Ca) has a valency of +2, it requires an anion with equivalent valency of -2. Nitrate ion (NO3) has a valency of -1 so it needs 2 molecules of it to satisfy the Calcium's +2 valency.

Carbonate (CO3) has -2 valency, so it replaces the 2 NO3 molecules by 1 of itself and bonds to Ca.

Sodium (Na) has +1 valency, so it is satisfied by 1 molecule of NO3 but there are 2 molecules of both Na and NO3. Therefore, we attach the stoichiometric coefficient of 2 to NaNO3.

mechanics (greek   is that area of science concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment. the scientific discipline has its origins in ancient greece with the writings of aristotle and archimedes[1][2][3] (see history of classical mechanics and timeline of classical mechanics). during the early modern period, scientists such as galileo, kepler, and newton laid the foundation for what is now known as classical mechanics. it is a branch of classical physics that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light. it can also be defined as a branch of science which deals with the motion of and forces on objects. the field is yet less widely understood in terms of quantum theory.

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