Given the following balanced equation, calculate the theoretical yield of h2 in grams if you start with 25.3g zn and have an excess of hcl. zn(s) + 2hcl(aq) → zncl2 (aq) + h2

   The  theoretical  yield  of H₂  in grams   is  =

  calculation

Zn(s)  + 2HCl(aq)  →     ZnCl₂(aq)  +H₂

Step 1:  find the  moles  Zn

moles = mass÷   molar mass

from periodic table the  molar mass  of Zn = 65.4 g/mol

moles is therefore = 25.3 g/65.4 g/mol=0.387   moles

Step 2:  use  the  mole ratio   to determine the  moles of H₂

from given  equation Zn:H₂ = 1:1 therefore the  moles of H₂  is also =0.387  moles

Step 3: find theoretical mass of H₂

mass=  moles×  molar mass

from  periodic table the  molar mass  of H₂ = 1 × 2 = 2 g/mol

mass =0.387  moles ×   2 g/mol =0.774 grams

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.