Question

2. Organ transplantation is often the only effective medical treatment for end-stage organ failure, but there is a huge shortfall in the number of organs available for transplant. One factor that contributes to this shortfall is the limited shelf life of organs. For example, donor hearts are typically stored on ice until the transplant procedure can be performed, but they only remain viable in this state for a few hours. Several research groups are exploring the possibility of prolonging organ shelf-life using cryopreservation. In one approach known as vitrification, the organs are equilibrated with high concentrations of cryoprotective agents (CPAs) and stored in liquid nitrogen at a temperature of -196 °C; the CPAs increase viscosity and allow the sample to be brought to -196 C without ice crystallization a. A human heart with a volume of 150 mL is bathed in 350 mL of cryopreservation medium consisting of 45% water and 55% dimethyl sulfoxide. The heart is initially at 25 °C. How much heat (in kJ) must be removed from the heart (and the surrounding medium) to bring it to a temperature of -196 °C? You can assume the entire system can be approximated as 500 mL of cryopreservation medium b. Assuming all of the heat lost from the heart (and the surrounding medium) results in vaporization of the liquid nitrogen, what volume of liquid nitrogen is converted to vapor You can assume that 5.6 kJ of heat is required to vaporize 1 mole of liquid nitrogen Liquid Nitrogen 196 "C Human heart (150 mL) in cryo medium (350 mL) 25 °C

Answer 1

Ans:

1. Heat released from heart = Q = mcΔT

Here m = 150 gm

C (Specific heat of nitrogen) = 0.2483 cal/gm⁰C

The amount of heat released is 8.231145 kcal = 34.46215 K joules

2. For finding vapore nitrogen, First we calculate how many moles in solution

So for that

We have density of liquid Nitrogen = 0.808 g/mL

Volume = 500 ml

Mass = 404 g (m=density * volume)

Molar mass (M) = 28.014 g/mol

Moles = 14.42 mol (n = m/M)

For 1 mol vapor it reqires 5.6 KJ energy, at 34.46215 KJ energy 6.15 mols of liquid Nitrogen converts into vapour.

Volume of vapor liquid nitrogen = 213.225 mL