Agraduated cylinder weighs 100.0 g. If you add 20.0 g of water and 10 pennies, the mass is now 149.5 g. What is the average mass of the added pennies?

Explanation:

the mass of water + mass  of cylinder + mass of pennies= 149.5 g

  20 + 100+10 X   = 149.5

10  X = The mass of the pennies = 29.5 g

 mass of one penny = 29.5 / 10

                                  = 2.95 g

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.