Tuesday, May 7, 2013

use the factor theorem to determine whether (x-3) is a factor of f(x)=x^4+12x^3+6x+27

use the factor theorem to determine whether (x-3) is a factor of f(x)=x^4+12x^3+6x+27
Answer
(x)=x  4  given that x-3 is a factor of expression
use remainder theorem
put x  - 3  = 0
we get x = 3
plug 3 in place of x in the given value of f (x)
f(x)=x⁴+ 12x³ + 6x + 27
f(3)=(3)⁴+12(3)³+6(3)+27.
     = 81+ 324 + 18 + 27
     = 430
here 430 is not equal to 0 so that  Hence x -3 is not a factor of f(x)=x^4+12x^3+6x+27

Tuesday, April 30, 2013

A coffee cup calorimeter contains 0.0375 mol HCl dissolved in 1.50 x 10^2 mL of water at 20.51 C. When 1.75 g of solid zinc metal is placed in the calorimeter, the temperature rises to 29.02 C. Assume that no heat is lost to the surroundings.

A coffee cup calorimeter contains 0.0375 mol HCl dissolved in 1.50 x 10^2 mL of water at 20.51 C. When 1.75g of solid zinc metal is placed in the calorimeter, the temperature rises to 29.02 °C.  Assume that no heat is lost to the surroundings.

Write the balanced equation for the reaction that takes place in the calorimeter.  1pt
Balanced reaction
Zn (s)  + 2 HCl (aq) --> ZnCl2(aq) + H2 (g)

Find the limiting reactant. Show your work. 2 pts.
Number of moles of Zn             = given mass of Zn / molar mass of Zn
                                                  = 1.75 g Zn / 65.3.9 g/mol
                                                  = 0.02676 moles Zn
In equation 1 mole of Zn react with 2 mol of HCl
Hence  0.02676 moles Zn react with        = 2  x 0.02676
                                                             = 0.05352 mol of HCl 
But required moles of HCl (0.05352 mol) > given moles (0.0375)
Hence HCl is limiting reagent

Find the amount of heat lost or gained by the calorimeter. Show your work. 2pts.
Formula of heat change, ∆T       = T2 - T1 = 29.02 - 20.51  = 8.51 ° C
Specific heat capacity for water , C = 4.184 J/g-C
Mass of water m                            = 1.50 x 102  ml = 150 g  (for water 1 ml = 1 g )
Use formula of enthalpy change ∆H = m * C *∆T
Plug the values
                                               ∆H = 150 g  x 4.184 J/g-C  x 8.51 C
∆H = 5341 Joules         
Divide by 1000 to convert in kJ 
                                                ∆H = 5.34 KJ
Temperature is increasing so that it is a exothermic reaction
And for all exothermic reaction ∆H is always negative 
energy lost by reaction and gained by solution.  hence calorimeter gain this energy
 So final answer will ∆H = - 5.34 KJ

Sunday, March 31, 2013

Which of the following pairs of linear equations are consistent/inconsistent? If consistent, obtain the solution graphically:


Which of the following pairs of linear equations are consistent/inconsistent? If consistent, obtain the solution graphically:
(i)              x + y = 5, 2x + 2y = 10
Convert the equation in form of 
a1x + b1y + c1 = 0  and a2x+ b2y + c2 = 0
We get
               x + y  -5 = 0, 2 x + 2 y  -10 = 0
Compare the equation with
              
We get
a1 = 1,            b1       = 1,                 and c1 = -5
a2 = 2             b2        = 2                   and c2 = - 10
                                    
 So we get 
                                  
Dependent and consistent  so it will have many solutions .
(ii)           x – y = 8, 3x – 3y = 16
Convert the equation in form of
a1x + b1y + c1 = 0  and a2x+ b2y + c2 = 0
We get
   x – y -8 = , 3x – 3y -16 = 0
Compare the equation with
                         
We get
a1 = 1,  b1     = - 1,              and c1 = - 8
a2 = 3  b2      =  - 3               and c2 = - 16
 
So we get 
  
So both lines are Inconsistent
(iii) 2x + y – 6 = 0, 4x – 2y – 4 = 0
Compare the equation with
              
We get
a1 = 2,            b1       =  1,                and c1 = - 6
a2 = 4             b2        =  - 2               and c2 = - 4
 
So we get 

So both lines are consistent
Solve the equations graphically
2x + y – 6 = 0,
Subtract 2x and add 6 both side we get
 y  = 6 – 2x
plug x = 1,2 and 3 we get
y         =  6 - 2 * 1      = 4
 y         = 6 -  2 * 2      = 2
y          =  6 -  2 * 3     = 0
X
1
2
3
y
4
2
0

 4 x – 2 y – 4 = 0
Divide by 2 we get
2 x – y - 2                  = 0 
Add y both side we get
2 x – 2            = y
or
y          = 2x – 2
plug x  = 1.2 and 3 we get
y          = 2 * 1 – 2      = 0
y          = 2 * 2 – 2      = 2
y          = 2 * 3 – 2      =  4
X
1
2
3
y
0
2
4

Answer x = 2 and y = 2

(iv) 2x – 2y – 2 = 0, 4x – 4y – 5 = 0
Compare the equation with
         
We get
a1 = 2,            b1       = - 2,              and c1 = - 2
a2 = 2             b2        =  - 2               and c2 = - 5
So both lines are Inconsistent