Draw and upload a picture of a concentration cell composed of two compartments with Zn/Zn2 as the components that will produce a voltage of 0.15 V. Be sure to include the following: (i) the concentration of Zn2 in each compartment; (ii) the composition of the electrodes in each compartment; (iii) the direction of electron flow; (iv) label the anode and the cathode compartments

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2

the answer is c.the valence of the atoms combine .