Which is considered an indication that a chemical reaction or chemical change has taken place a: solid melts b: heat is given off c: substance dissolves d: substance change shape

B: heat is given off C:

Explanation:

Physical Change                                                                                              

The changes that occur only due to change in shape or physical properties but their chemical or internal composition remain unchanged.  

These changes were reversible.

They have same chemical property.

These changes can be observed with naked eye.

Example :

Water converting to Ice

Water converting to gas

Chemical change:

The changes, that occur due to change in the composition of a substance and result in a different compound is known as chemical change.

These changes are irreversible

These changes occur due to chemical reactions

These may not be observed with naked eye

Example:

Combustion of fuel or wood: that oil or wood convert into energy, CO2 and ash in case of wood

So in given data the heat is given off indicate the chemical change while others

Solid melts

Substance dissolve

Substance change shapes are physical changes because no new product is obtained there is no indication of chemical reaction.

in the given question, the partial pressure is calculated by using the ideal gas equation, that is, pv = nrt

here, p is pressure, v is volume = 25 l, n is number of moles = 0.0104 moles, r is gas constant = -0.0821 l.atm / mol.k

t is temperature = 273 k

p = nrt / v

p = (0.0104 mol × 0.0821 l.atm / mol.k × 273 k) / 25 l

= 0.0093 atm