For a fixed amount of real gas when a graph of `z v//s` p was plotted than at very high pressure slope was observed to be `0.01 atm^(-1)`. At the same temperature if a graph is plotted b//w pv v//s `P` then for 2 moles of the gas 'Y' intercept is found to be 40 atm-litre. calculate excluded volume in litres for 20 moles of the real gas.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Understand the Van der Waals Equation
The Van der Waals equation for real gases is given by:
\[ \left(P + \frac{n^2a}{V^2}\right)(V - nb) = nRT \]
Where:
- \( P \) = pressure
- \( V \) = volume
- \( n \) = number of moles
- \( R \) = universal gas constant
- \( T \) = temperature
- \( a \) = measure of attraction between particles
- \( b \) = excluded volume per mole of gas (what we need to find)

### Step 2: Analyze the First Graph (Z vs. P)
At very high pressures, the term \( \frac{n^2a}{V^2} \) becomes negligible. Thus, we can simplify the equation to:
\[ P(V - nb) = nRT \]
Rearranging gives:
\[ PV = nRT + Pnb \]
From this, we can express the compressibility factor \( Z \):
\[ Z = \frac{PV}{nRT} \]
At high pressures, we can assume:
\[ Z = 1 + \frac{Pb}{RT} \]
Given that the slope of the graph \( Z \) vs. \( P \) is \( 0.01 \, \text{atm}^{-1} \), we can equate this to:
\[ \frac{b}{RT} = 0.01 \]
This is our Equation (1).

### Step 3: Analyze the Second Graph (PV vs. P)
From the problem, we know that the y-intercept of the graph of \( PV \) vs. \( P \) for 2 moles of gas is \( 40 \, \text{atm-litre} \). The equation for this graph can be expressed as:
\[ PV = nRT + Pb \]
For \( n = 2 \):
\[ PV = 2RT + Pb \]
The y-intercept corresponds to \( 2RT \), thus:
\[ 2RT = 40 \quad \Rightarrow \quad RT = 20 \]
This is our Equation (2).

### Step 4: Substitute and Solve for b
Now we can substitute \( RT = 20 \) into Equation (1):
\[ \frac{b}{20} = 0.01 \]
Solving for \( b \):
\[ b = 0.01 \times 20 = 0.2 \, \text{litres} \]

### Step 5: Calculate the Excluded Volume for 20 Moles
The excluded volume \( B \) for \( n \) moles is given by:
\[ B = n \cdot b \]
For \( n = 20 \):
\[ B = 20 \cdot 0.2 = 4 \, \text{litres} \]

### Final Answer
The excluded volume for 20 moles of the real gas is:
\[ \boxed{4 \, \text{litres}} \]