Question

1. How many calories are required to melt 25 g of ice, heat the liquid from 0 C to 100 C and boil the liquid?

		18,000 cal
		29,500 cal
		6,500 cal
		26,000 cal 2. Scope mouthwash is a(n) homogeneous mixture compound element heterogeneous mixture 3. How many calories are needed to heat 25 g of water from 15 C to 27 C? 110 cal 0.48 cal 300 cal 2.1 cal

Answer 1

specific heat of fusion of water 333.55 J/g

to convert 0 degree Celsius ice to 0 degree Celsus 25 g water = 333.55 x 25 = 8338.75 J

then we have to increase the temperature from 0 degree Celsius 25 g water to 100 degree Celsius water

specific heat of water 4.184 J/g

energy required = 4.184 x25x 100 = 10460 J

boiling means 100 degree Celsius water to 100 degree Celsius steam

specific heat of vaporaisation = 40650/18 x 25= 56458.33 J

on adding all these = 75257.08 J

on converting it to Calories = 75257.08/4.184 = 17986 Cal which is approximately equal to 18000 Cal is the correct answer

2. Generally, mouthwashes are a homogeneous mixture of a certain percentage of alcohol along with a variety of different chemicals.

A homogeneous mixture is a mixture which contains the same composition throughout the mixture.

3. Specific heat of water is 4.184 J = 1 Cal

mass of water =25 g

change temperature = 27-15 = 12 degree Celsius

energy required = 25*1*12= 300 Cal

300 Cal is the correct answer.