What is the total amount of heat required to completely melt 347 grams of ice at its melting point?
1)334 j
2) 1450 j
3) 116,000 j
4) 784,000 j

The correct answer is Option C.

Explanation: The heat required can be calculated by using the formula:

where, q = heat required or released

m = mass of the substance

L = Latent heat

As, this process is the melting of ice, so latent heat of fusion is used:

Latent heat of fusion for ice is 334 kJ/kg

Mass of the object = 347 grams = 0.347 kg  (Conversion factor: 1kg = 1000 grams)

Putting the values in above equation, we get:

Converting kilo-joules into joules, we use the conversion:

1 kJ = 1000J

So, q = 116000J

Hence, the correct option is 3.

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