Atypical ice cube has a volume of about 16.0 cm3. calculate the amount of energy needed to melt the ice cube. (density of ice at 0.°c = 0.917 g/ml; molar enthalpy of fusion of ice = 6.009 kj/mol; molar mass of h2o =18.02 g/mol.)

6.009*10^3 /18.016

=4.89KJ

so 4.89 KJ is needed

the answer is d. 74.02

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