5
- hcn +
cuso4 →
type of reaction

Explanation:

The valancy of Cu = +2

SO4 = -2

CN = -1

H =+1

So when HCN and CuSO4 react Cu(CN)2 and H2SO4 are formed.

Cu(CN)2 formation :

2 CN = 2 x -1  = -2

Its should attach to +2 charge atom which is Cu

So 1 Cu and 2 CN = Cu(CN)2

Similary,

H2SO4 formation:

SO4 = -2 charge

It require +2 charge so need two H+

2 H = 2x1 = +2 charge

Hence , 1 SO4 and 2 H combine to form H2SO4

Law of conservation of mass: It states that mass can neither be created nor destroyed during a chemical reaction.

Total mass of the reactant must be equal to total mass of product.

Only those equations are balanced which follows law of conservation of mass

Count total number of atoms in the reactant and product .

The number of atoms in the product = The number of atoms in the reactant

In the given equation:

Reactant are 2HCN and CuSO4

atoms of H = 1x2=2 , C=1x2=2  , N=1x2=2 , Cu = 1, S = 1 ,O =4

Products: Cu(CN)2 and H2SO4

atoms of H =2 , S=1 , O=4 ,C = 2x1=2 , N = 2x1 =2 , Cu = 1

Hence this is balance equation

when 25.0 ml of 0.700 mol/l naoh was mixed in a calorimeter with 25.0 ml of 0.700 mol/l hcl, both initially at 20.0 °c, the temperature increased to 22.1 °c. the heat capacity of the calorimeter is 279 j/°c.

the equation for the reaction is:

naoh + hcl → nacl + h₂o

moles of hcl = 0.0250 l hcl ×

0.700

mol hcl

1 l hcl = 0.0175 mol hcl

volume of solution = (25.0 + 25.0) ml = 50.0 ml

mass of solution = 50.0 ml soln ×

1.00

ml soln

= 50.0 g soln

δt=t2-t1

= (22.1 – 20.0) °c = 2.1 °c

the heats involved are

heat from neutralization + heat to warm solution + heat to warm calorimeter = 0

q1+q2+q3=0

nδh+mcδt+cδt=0

0.0175 mol ×

δh

+ 50.0 g × 4.184 j·g⁻¹°c⁻¹ × 2.1 °c + 279 j°c⁻¹ × 2.1 °c = 0

0.0175 mol ×

δh

+ 439.32 j + 585.9 j = 0

0.0175 mol ×

δh

= -1025.22 j

δh=1025.22j0.0175 mol= -58 600 j/mol = -58.6 kj/mol