Question

The specific heat of copper is 0.385 J/(g∙°C). If 34.2 g of copper, initially at 25°C, absorbs 4.689 kJ, what will be the final temperature of the copper?

a. 25.4°C b. 27.8°C c. 356°C d. 381°C

A chemical reaction causes the temperature of 1.0 x 102 g of water in a calorimeter to rise from 25°C to 40°C. The specific heat of water is 4.184 J/(g∙°C). What is the heat of reaction, qP?

a. -0.31 kJ b. -0.75 kJ c. -1.5 kJ d. -6.3 kJ 13. The standard enthalpy of formation for water vapor is ΔH°f = -241.8 kJ/mol.

Write out the standard formation reaction for water vapor in terms of a balanced thermochemical equation.

a. H2O (l) → H2O (g) ΔH°f = -241.8 kJ/mol     b. H2O (g) → H2 (g) + ½ O2 (g) ΔH°f = -241.8 kJ/mol      c. 2 H2 (g) + O2 (g) → 2 H2O (g ΔH°f = -241.8 kJ/mol d. H2 (g) + ½ O2 (g) → H2O (g) ΔH°f = -241.8 kJ/mol

Please show work

Answer 1

The specific heat of copper is 0.385 J/(g∙°C). If 34.2 g of copper, initially at 25°C, absorbs 4.689 kJ, what will be the final temperature of the copper?

a. 25.4°C b. 27.8°C c. 356°C d. 381°C

Answer- q = mcat
4689 J = (34.2)(0.385 J/gC)(X-25)
356 = X-25
X = 381

d. 381°C

A chemical reaction causes the temperature of 1.0 x 102 g of water in a calorimeter to rise from 25°C to 40°C. The specific heat of water is 4.184 J/(g∙°C). What is the heat of reaction, qP?

a. -0.31 kJ b. -0.75 kJ c. -1.5 kJ d. -6.3 kJ 13. The standard enthalpy of formation for water vapor is ΔH°f = -241.8 kJ/mol.

Answer- q = (4.18 J g^-1 K^-1)*(100g)*(313-298 K)

q = 6.27 kj

= -6.3 kj

Write out the standard formation reaction for water vapor in terms of a balanced thermochemical equation.

a. H2O (l) → H2O (g) ΔH°f = -241.8 kJ/mol     b. H2O (g) → H2 (g) + ½ O2 (g) ΔH°f = -241.8 kJ/mol      c. 2 H2 (g) + O2 (g) → 2 H2O (g ΔH°f = -241.8 kJ/mol d. H2 (g) + ½ O2 (g) → H2O (g) ΔH°f = -241.8 kJ/mol

Answer-

d. H2 (g) + ½ O2 (g) → H2O (g) ΔH°f = -241.8 kJ/mol

Answer 2

The molar heat capacity of an unknown substance is 92.1 J/mol-K. If the unknown has a molar mass of 118 g/mol, what is the specific heat (J/g-K) of this substance?
A) 1.28