CHEM 1050 Lecture Notes - Lecture 6: Hydrazine, Styrofoam, Heat Capacity

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orchidkangaroo311

24 Sep 2016

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Day 6: heat in the dry labs, be very careful with decimal places! homework // will be on midterm [similar to 6. 119] for caco3(s) cao(s) + co2(g) Material for midterm #1 [october 5th] from sept. 9th - oc. Molar heat capacity: the amount of heat needed to produce a change of 1 c in 1 mole of something q = n(c)( t) n = number of moles, c = molar heat capacity, t = temperature change. ** things with low heat capacity don"t heat up as much [i. e. styrofoam cups] do 6. 147 [final] where you use specific heat concept: q = s(m)( t) s = specific heat, m = mass [in grams] H2o(l) is 4. 184 j/ c(g) [very high] e. x. 1 gram of benzoic acid [formula found in dry lab] produces 26. 38 kj of heat. We see that temperature increases by 5. 022 c. What is the heat capacity of the calorimeter? (26. 38 kj / 5. 022 c) = c.

Related Questions

When 0.595 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 25.4 âC to 29.9 âC.

Part A

Find ÎErxn for the combustion of biphenyl in kJ/mol biphenyl. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 5.86 kJ/âC.

Part B

Learning Goal: To understand the concepts of heat capacity, specific heat, and molar heat capacity. Heat capacity, C, is the amount of energy required to raise the temperature of a substance by exactly 1 degree Celsius. The energy needed to warm an object increases as the mass of that object increases. We see this in our everyday life. For example, we know that it takes much more energy to heat a large tank of water than a small cup. Because of this dependence on mass, experimentally determined heat capacities are always reported in terms of the amount of the substance that is heated. One method is to report how much energy it takes to raise the temperature of one mole of a substance by exactly 1 degree Celsius. This value is the molar heat capacity, which has the symbol Cp.The molar heat capacity is given in the units J/(molâ âC). A second method is to report how much energy it takes to raise the temperature of one gram of a substance by exactly 1 degree Celsius. This value is the specific heat, which has been given the symbol Cs. The units for specific heat are J/(gâ âC). The heat capacity of a substance is therefore related to the energy q needed to raise its temperature by an amount ÎT. That is, q=nCpÎT, where n denotes the number of moles of the substance, or q=mCsÎT, where m denotes the number of grams of the substance.

Part 1

It takes 55.0 J to raise the temperature of an 9.90 g piece of unknown metal from 13.0âC to 24.8 âC. What is the specific heat for the metal?

Express your answer with the appropriate units.

Part 2

The molar heat capacity of silver is 25.35 J/molâ âC. How much energy would it take to raise the temperature of 9.90 g of silver by 16.0 âC?

Express your answer with the appropriate units.

Part 3

What is the specific heat of silver? Express your answer with the appropriate units.

pearcockroach968

To understand the concepts of heat capacity, specific heat, andmolar heat capacity.
Heat capacity, C, is the amount of energy required to raise thetemperature of a substance by exactly 1 degree Celsius. The energyneeded to warm an object increases as the mass of that objectincreases. We see this in our everyday life. For example, we knowthat it takes much more energy to heat a large tank of water than asmall cup. Because of this dependence on mass, experimentallydetermined heat capacities are always reported in terms of theamount of the substance that is heated. One method is to report howmuch energy it takes to raise the temperature of one mole of asubstance by exactly 1 degree Celsuis. This value is the molar heatcapacity, which has the symbol C_p.The molar heat capacity is givenin the units \rm J / mol \cdot{}^\circ C. A second method is toreport how much energy it takes to raise the temperature of onegram of a substance by exactly 1 degree Celsius. This value is thespecific heat, which has been given the symbol C_s. The units forspecific heat are \rm J / g \cdot{} ^\circ C.

The heat capacity of a substance is therefore related to the energyq needed to raise its temperature by an amount Delta T. That is, q= nC_{\rm p}\Delta T, where n denotes the number of moles of thesubstance, or q = mC_{\rm s}\Delta T, where m denotes the number ofgrams of the substance.

Part A
It takes 53.0 J to raise the temperature of an 8.10 g piece ofunknown metal from 13.0 C to 24.0 C. What is the specific heat forthe metal?
Express your answer numerically, J/g*C

Part B
The molar heat capacity of silver is 25.35 j/mol*C. How much energywould it take to raise the temperature of 8.10 g of silver by 13.8C?

Part C
What is the specific heat of silver?

1. Complete and balance the following chemical reaction: NH4NO3(s) + H2O(l) --> ?

Given

2. Volume of DI water used 50 mL

3. Mass of DI water 50 g

4. Initial temperature of water, Ti 22.5Â°C

5. Mass of NH4NO3 3.0 g

6. Moles of NH4NO3 ________0.0375__________mol

7. Final temperature of water, Tf 18.9Â°C

8. change in temperature of the water (?T) -3.6 Â°C

9. calculate the heat associate with water, qH2O ___ ___-752.4_____________ J

m*c* deltaT = (50g)(4.184 J/g*k)(-3.6) = -752.4

10. the heat either released or absorbed by the reaction (?Hrxn) ________+752.4____________ J

Question: [Please notice the units]

11. Calculate the change in enthalpy (?Hrxn) for this reaction. _____________ kJ ??

12. Calculate the heat of reaction in kJ per mole of NH4NO3 ______________ kJ/mol ??

13. If the heat capacity of the calorimeter was 25 J/oC, what would the new change in enthalpy (?Hrxn) for this reaction be? (Use equation 7 to recalculate the value from #10) ____________________ kJ/mol ?? [Equation 7: - q(rxn) = q(soln) + q(calorimeter)

14. Is this an exo- or endothermic reaction? Explain the reasoning behind your choice. ??

15. Calculate the change in enthalpy for the reaction (?Hrxn) per mole using equation 8 and Table 2. NH4NO3 (s) --> NH4NO3 (aq)

__________________kJ/mol ?? [Equation 8: ?H_rxn = sum{ n?H_f (products) - sum{ n?H_f (reactants)

16. What is the percent error between your value and the value calculated from 13? What are some possible sources of error in the experiment?

__________________% error

CHEM 1050 Lecture Notes - Lecture 6: Hydrazine, Styrofoam, Heat Capacity

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