A1.75-cm diameter naphthalene mothball is suspended in an air stream at 280 k, 1.0 atm, and constant velocity of 1.4 m/s. solid naphthalene exerts a vapor pressure of 2.8 pa at 280 k. consequently, the naphthalene very slowly sublimes into the passing air stream, with the rate limited by convective mass transfer. the density of solid naphthalene is 1.14 g/cm3, and the molecular weight is 128 g/mole. a. what is the initial evaporation rate of naphthalene mothball? b. how long will it take for the mothball to shrink to half of its original diameter? remember: as the mothball shrinks, its diameter is decreasing, which in turn affects the reynolds and sherwood numbers.

false

because it does not have the potential to be entirely used up

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements