Homework Help: Chemistry

Posted by Ashley on Saturday, April 30, 2011 at 1:57pm.

So I am writing a lab report and Im stuck with calculating the enthalpy change of combustion of the following reaction:
Mg+2HCl--> MgCl2+H2 .I am given the mass of Mg which is 5g and the concentration of HCl which is 2M and the volume of HCl which is 50 cm^3.I found the limiting reactant which was HCl and i have to measure the ÄÇ of combustion..I know that HE(HEAT ENERGY)=m x c x ÄT and the change in temperature is 10 degrees celsius. I also know that in order to find ÄH we divide HE with n which is the number of moles of the limiting reactant..can anyone please help me find the ÄH?i DONT know whose mass to use, i know i have to use the heat capacity of water..and i dont know whether i have to convert temperature into Kelvin measurement.

Chemistry - DrBob222, Saturday, April 30, 2011 at 2:27pm
Frankly, I don't know how you are to calculate heat of combustion when you didn't combust Mg but reacted it with HCl instead.
You measured the T difference of the water; therefore, find the q from mc*delta T by using the mass of water (50 cc = 50g if the density is 1.00 g/cc) and the specific heat of water.
Chemistry - Ashley, Saturday, April 30, 2011 at 3:09pm
we were asked to find the enthalpy change because it is an exothermic reaction. Dont i have to convert cm^3 into dm^3 in the equation?when i divide the Heat energy with the number of moles in order to get enthalpy change do i put the moles of the limiting reagent?
Chemistry - DrBob222, Saturday, April 30, 2011 at 4:59pm
You want the mass of the water and the volume of the water is 50 cc. Since the density is 1.00 g/cc, the mass is 50 g. You CAN convert cc to dm^3 if you want to use a different value for density in g/dm^3. After finding q, then delta H rxn = q/n for the limiting reagent which gives J/mol for the unit.

Answer this Question

Related Questions

Chemistry - I'm trying to calculate the enthalpy of the reaction Mg(s) + ...
Chemistry - It's a molar heat reaction lab. 0.07g Mg Mg+2HCl->MgCl2+...
Chemistry - Recognize each of the following reactions as synthesis, ...
Chemistry - Mg(s) + 2HCl(aq) -> MgCl2(aq) + H2(g) delta H1? MgO(s) + 2HCl...
Chemistry - Can someone tell me if I have this correct, I am leaving something ...
chemistry - consider the following reaction: Mg(s)+ 2HCl(aq) --> MgCl2 (...
Chemistry - Mg + 2HCl -> MgCl2 +H2 delta H = ? MgO + 2HCl (aq) -> ...
Chemistry! - a)consider the following reaction: Mg(s)+ 2HCl(aq) --> MgCl2...
Chemistry - How many mole of H2 will be produced if 0.500 grams of magnesium is ...
Ap chem question 2 related to the first question - Calculate the volume of gas ...

For Further Reading

First Name:
School Subject:
Answer: