(really need 30 points )if the mass of a material is 12 grams and the volume of the material is 49 cm^3, what would the density of the material be? and it's not 4.08 g/cm3

The answer is 0.25 g/cm3

The equation for finding density is mass divided by volume.

Therefore,

         12 grams/ 49 cm3= 0.24489795918367 gram/cubic centimeter

               you would then round this to the nearest significant figure which is the number of significant numbers you have and the highest amount of sig figs present in this equation is two sig figs. That means that you would round your answer, becasue it has a zero before the decimal which doesn't count as a significant figure, to the nearest hundredth which would be 0.25 and then you add your value after it which is g/cm3

Density = mass/volume

Density = 12g/49cm^3

Density = 0.24 g/cm^3

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.

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