In a chemical reaction, the reactants are substances that undergo the reaction, and the products are substances that are formed during the reaction. The table below shows the reactants and products of several different chemical reactions. Reactants Products Type of Reaction
4K + O2 2K2O + heat Exothermic
2H2O + heat 2H2 + O2 Endothermic
2CO + O2 2CO2 + heat Exothermic
CaCO3 + heat CaO + CO2 Endothermic

Based on the information given in the above table, the best definition of an endothermic reaction would be
A.
a reaction that absorbs heat.
B.
a reaction that has one product.
C.
a reaction that does not require heat.
D.
a reaction that releases heat.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.

i think its 100.

hope this !

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.