## Filling a Leaking Tank

A 1000ft3 tank is being filled with water at a rate of 1.04 L/min. How long (seconds) will it take to half fill the tank if there is a leak rate of 4.10 ml/s?

A) 1.07*106 s B) 2.14*106 s
C) 1.34*104 s D) 3.88*104 s
This problem can easily be solved through a mass balance on the tank. In this scenario there are no generation or consumption of the water, thus reducing the conservation of mass formula to:

$Accumulation = Input - Output$

This question also involves the proper conversion of units. Visit the formula tab for conversion factors.

Conservation of mass formula:
$Accumulation = Input + Generation - Output - Consumption$ 1ft^3=28.317L

Solution

## Excess Reactants

Ammonia and Oxygen gas can be reacted together to form Nitric Oxide and Water as shown:
4NH3 + 5O2 = 4NO + 6H2O

If 100kg/day of Ammonia and 200kg/day of Oxygen gas are fed into a reactor, what is the percentage by which the excess reactant is in excess?

Use the following molecular weights:
17g/mol NH3
32g/mol O2

A) 50% B) 34%
C) 18% D) 15%
Use the molecular weight of each reactant to convert mass to moles. Using the stoichiometric relationship given by the chemical reaction, find the theoretical amount of reactant needed to complete the reaction.
To convert mass into moles: moles=mass/molecular weight
To calculate excess: excess=(fed-reacted)/fed

Solution

## Understanding the Ideal Gas Law

An ideal gas is contained in a hot closed rigid cylinder. If the gas is further compressed, what will happen to the temperature of this gas?

A) Increases B) Remains the Same
C) Decreases D) Impossible to Predict
Use the ideal gas law to understand the relationship between the variables. No need to use actual numbers.

Ideal Gas Law:
$PV=nRT$

Solution

## Understanding Dimensions Part 1

Suppose the density of a unknown fluid is given by the equation:

ρ=AeB*P

where ρ has units of g/L and P has units of atm. What are the units of A and B respectively?

A) g/L ; atm-1  B) g/L ; B is unitless
C) g/L ; atm   D) A and B are unitless

For an equation to be valid, dimensional homogeneity must exist. Also an exponent must be unitless!

There are no formulas needed to solve this question.

Solution

## Concept of Entropy

Which of the following statements are true regarding entropy?

i) Entropy of the universe is always increasing
ii) Entropy of the system is always increasing
iii) For a reversible process, Entropy of the universe is zero
iv) Freezing liquid water would cause a decrease in the Entropy of the system
v) Entropy is a state function

A) i, ii, v  B) iii, iv, v
C) i, iii, v  D) i, ii, iv
There are no hints for this question.
There are no necessary formulas needed for this question.

Solution