We often use grinding in closed circuit, and have a targeted value for a circulated load. What is the formula for the percentage circulating load? Explain why a circulating load is preferable to just grinding until we are sure that everything would pass through the post grinding screen.

You have been given a piece of steel but you do not know its composition. Describe the process you would use to harden it?

5. Explain the changes to the ecosystem that arose with the exclusion of grey wolves from the ecosystem. Describe how Society developed successful strategies to sustain healthy populations of the wolves given the potential conflict. (5 marks)

What is the energy consumption per kilogram of zinc in an electrowinning operation with a current density of 250 Amps/m2 assuming 95 % efficiency, n = 2, and a voltage drop of 3.0 volts across the cell? HINT: Current density is the current available divided by unit area of cathode. It includes BOTH sides of the immersed cathode.

5.One kilogram of superheated steam at 350°C and 20 bar absolute pressure are sealed in a rigid container. Cold water is sprayed on the container until the temperature is 50°C. (Remember that the container is rigid, so the total volume doesn’t change.) a) What is the volume of the container in liters? (Do not assume ideal gas behavior.) Liters b) Is the correct energy balance for this problem based on energy or enthalpy? (answer either enthalpy or internal energy) c) What is the final pressure inside the container (in Pascals)? Pa d) How much of the initial water condenses (g), if any? g e) How much heat was removed from the container while it was being cooled (kJ)? kJ f) How much work was done while the container was being cooled (kJ)? kJ.

1. One kilogram of liquid water at 75°C is heated in a frictionless piston at a constant pressure of 5 bar. A total of 2750.7 kJ of heat is added. For each answer, just put the number in the blank without units, and round to the nearest whole number (no decimals). And remember that "water" can mean liquid or vapor. a) What is the final temperature of the water in °C b) What is the final volume of the water in liters c) How much work was done in kJ d) What is the total change in internal energy (∆U) of the water in kJ.

An ODE for Newton’s law of cooling, ??/?? + ?? = ??(?) relates indoor temperature changes u(t) to outdoor temperature changes modeled by the function ?(?) = ? + ? cos(??) + ? sin(??). k is a constant that measures how well a building is insulated and t is time in hours. Suppose your air-conditioner is broken. You want to find out how outdoor temperature effects the temperature in your house by doing the following:

(a) Find a model for outdoor temperature, A(t). Specifically find a, b and c. Use ω = π/12 for a 24-hour time period. Use estimates of the high and low temperature of your current location. Assume the high temperature occurs at 4 pm.

(b) Solve the ODE above for u(t). Use k = 0.3 (a typically insulated building) and your equation from part (a). Use u(0) = temperature at midnight in your location for the initial condition.

(c) Create a graph with both your solution function and the outdoor temperature function.

(d) When does the maximum indoor temperature occur?

Suggest method how porosity of the particles can be obtained experimentally.

Pure gaseous hydrogen at 10 atm is stored in a 10-cm-diameter, spherical steel pressure vessel having a wall thickness of 3 mm. The solubility of H2 in steel under these conditions is 0.085 m3 (STP)/(m3 of solid . atm) and the diffusivity of H2 in steel at 300oC is 3.8x10-10 m2 /s (independent of pressure). You may assume that the H2 partial pressure outside the vessel is zero.

a) Calculate the steady–state rate of leakage (in kmol/h) of H2 from the vessel.

b) Calculate the time in hours for the pressure inside the vessel to decrease to 9 atm, assuming the temperature stays constant at 300oC.

Multicomponent Distillation 1

A distillation column is separating ethane, propane, and n-butane at 5 atm. Operation is at total reflux. We want a 98.9% recovery of ethane in the distillate and a 99.8% recovery of n-butane in the bottoms. Propane is a sandwich component (e.g., in between light and heavy keys). The feed is a saturated liquid at 100 kmol/h composed of 30.0 mol% ethane, 33.0 mol% propane and 37.0 mol% n-butane. You may assume relative volatilities are constant, α_EB = 13.14, and α_PB = 3.91.

a) At total reflux find NMIN.

b) At total reflux find the fractional recovery of propane in the distillate.

c) At total reflux find distillate flowrate D.

Explain the procedure to select a low-pressure separator for a low gas-oil ratio well.

Mention all the steps and equations/tables/charts to be used in the selection process

The chlorination of methane is used to produce methyl chloride gas (CH3Cl) as a main product. In this reaction, the methane gas (CH4) reacts with chlorine gas (Cl2) to generate methyl chloride gas (CH3Cl) and hydrogen chloride gas (HCl) as well. Based on this information of reaction, you are asked to predict the product gas composition if the fractional conversion of the limiting reactant is 0.67 and the feed gas composition is 40 % CH4, 50% Cl2 and 10 % N2 (nitrogen). Assume 100 mol gas is fed to the reactor. (a) Develop the chemical reaction equation of chlorination of methane and process flow diagram as well. (b) Can you deduce a complete reaction occurs? Explain. (c) With calculation evidence, propose the limiting and excess reactant of the reaction and the percentage of excess reactant. (d) Perform the calculation to determine the product gas composition (%).

Consider the reaction NH4Cl(aq)NH3(g) + HCl(aq) The standard free energy change for this reaction is 62.8 kJ.

The free energy change when 1.72 moles of NH4Cl(aq) react at standard condition is____ kJ.

What is the maximum amount of useful work that the reaction of 1.72 moles of NH4Cl(aq) is capable of producing in the surroundings under standard conditions?_______

If no work can be done, enter none. kJ

You can make a snowball by packing snow together using hand pressure. The effect of this pressure increase is to partially liquefy the ice, which then re-freezes to hold the snow together. By comparing the phase diagrams of water and CO₂, determine whether it is possible to make analogous "dry ice balls."