Which is the best example of the law of conservation of energy? a basketball stops bouncing because its energy disappears. a rolling skateboard slows down because some of its kinetic energy changes to heat. a falling book hits the ground and all of its energy is destroyed. a toy car gains speed as it moves down a ramp because the ramp creates energy.

second choice, a rolling skateboard slows down because some of its kinetic energy changes to heat.

Explanation:

The law of conservation of energy states that energy cannot be created or destroyed ,but it remains constant and may be transferred or transformed into different kinds of energy.

Some kind of energies are gravitational potential energy, elastic potential energy, chemical energy, kinetic energy and heat energy, amond others.

Kinetic energy is the energy due to motion and is equal to ¹/₂ mv² . Hence a rolling skateboard has kinetic energy. This kinetic energy is converted to heat (not destroyed) due to friction between the wheels and the ground, so it slows down: conversion of kinetic energy into heat is a example of the law of conservation of energy.

On the other hand, the other statements, i) a basketball stops bouncing because its energy disappears, ii) a falling book hits the ground and all of its energy is destroyed, and iii) a toy car gains speed as it moves down a ramp because the ramp creates energy, do not represent examples of the law of conservation of energy since they state that the energy is either destroyed or created, in violation of the law of conservation of energy.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"