PLS HELP :,) Explain why zinc (Zn) would react with lead nitrate (PbNO3) but not with calcium chloride (CaCl2)

Zn metal can reduce the Pb metal that is on the right but cannot reduce the Ca metal on the left. of voltaic series

In the redox reaction, it is also known  

Reducing agents are substances that experience oxidation  

Oxidizing agents are substances that experience reduction

The metal activity series is expressed in voltaic series  

Li-K-Ba-Ca-Na-Mg-Al-Mn- (H2O) -Zn-Cr-Fe-Cd-Co-Ni-Sn-Pb- (H) -Cu-Hg-Ag-Pt-Au  

The more to the left, the metal is more reactive (easily release electrons) and the stronger reducing agent  

The more to the right, the metal is less reactive (harder to release electrons) and the stronger oxidizing agent

So that the metal located on the left can push the metal on the right in the redox reaction  

If we look at this voltaic series, it can be shown that Zn metal is located to the right of Ca metal and to the left of Pb metal, so that Ca metal has the strongest reducing power of the three metals and Pb has the strongest oxidizing power.

Thus, Zn metal can reduce the Pb metal that is on the right but cannot reduce the Ca metal on the left.

The reaction:

Zn + Pb(NO₃)₂ ⇒ Zn(NO₃)₂ + Pb

Zn ⇒ Zn²⁺ + 2e (oxidized)

Pb²⁺+2e⇒ Pb (reduced)

Zn + CaCl₂ ≠

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.