Question

3. When 10 mL of 2.0 M HCl is combined with 30 mL of 0.667 M NAOH a temperature change of 6.9 °C was observed. How much heat was given off per mole of water produced? ASsume the volumes are additive and that this NaCl solution has a density of 1.02 g/mL and a specific heat of 4.00 J/g-C. 2. How much heat is needed to change 32 g of 4.A 0.865 g sample of candy is burned in a bomb calorimeter whose heat capacity is 10.1 KJ°C. The temperature increases from 23.10 °C to 24.95 °C. Calculate the heat of combustion per gram of the candy. 5. Calculate AH for the reaction 2C(s)+H2(g)C2H2(g) given the following information: 2C2H2(g)+502(g)4CO2(g) + 2H20 (I) C(s)+O2(g) CO2(g) 2H2(g)+O2(g)2H2O(l) AH-2599.2 kJ AH -393.5 kJ AH-571.6 kJ 6. Complete combustion of one mole of benzene liquid, CH(l), releases 3267 kJ of heat (AH=-3267 kJ). Calculate the standard enthalpy of formation for benzene. Show work. 7.A coffee cup calorimeter contains 150 g of water at 25.1 °C. A 121 g block of solid copper is placed into the water and the temperature of the water and block goes to 30.1 °C. What was the initial temperature of the copper block? The specific heat of solid copper metal is 0.385 J/g-°C and the specific heat of water is 4.184 J/g-°C. Assume that the calorimeter doesn't absorb any heat

Answer 1

Q 3 ). HCl ( aq ) + NaOH ( aq ) $\rightarrow$ NaCl ( aq ) + H₂O ( l )

moles of HCl = ( 2 mol / litre ) x ( 10 x 10^-3 litre ) = 0.02 mol

moles of NaOH = ( 0.667 mol / litre ) x ( 30 x 10^-3 litre ) = 0.02 mol

total volume = 10 + 30 = 40 mL

mass of solution = density x volume = ( 1.02 gm / mL ) x 40 mL = 40.8 gm

heat evolve by 0.02 mol water = m x s x $\Delta$T = ( 40.8 gm ) x ( 4 J / g⁰C ) x 6.9 ⁰C

= 1126.08 J = 1.126 KJ

heat evolve by 1 mol water = 1.126 KJ / 0.02 mol = 56.3 KJ / mol