What is the change in internal energy if 30 J of thermal energy is released from a system, and the system does 40 J of work on the surroundings? Use U = Q - W. A. 70 J B. 10 J C. -10 J D. -70 J

The correct answer to the following question will be Option C (-10 J).

Explanation:

The given values are:

Work done by the system, W = 40 J

Thermal energy, Q = 30 J

Change in internal energy, U = ?

As we know,

⇒  

On putting the values in the above expression, we get

⇒  

⇒      

So that the change in internal energy will be "-10 J".

  1.the balanced   chemical equation is as below

cu +   2 ag(no)₃ → cu(no₃)₂   +2 ag

2.the   much silver   produced   is   50.9 g

step 1: find the   moles of cu

moles =   mass÷   molar mass

  from periodic table the molar mass of cu = 63.5 g/mol

moles is therefore = 15.00 g÷ 63.5 g/mol = 0.236   moles

step 2: use the mole ratio to determine the   moles of ag

from equation above   cu: ag   is 1: 2

therefore the moles of ag   =0.236   moles   x 2/1 =0.472   moles

step 3: find the mass   of ag

mass = moles x molar mass

from periodic table   the molar mass of ag =107.87 g/mol

mass   = 0.472   moles x 107.87 g/mol = 50.9 g

3.   the   much   silver   collected worth is   1.797 oz

  convert   50.9 g   to oz

that is   1 gram = 0.0353 oz

          50.9 grams =?   oz

by cross multiplication

={(50.9 grams x 0.0353 oz) / 1   gram}   =1.797 oz