While you were "sweating" your chemistry test, water vapor evaporates from your body, absorbing 50,000 J of energy. (assume no temperature change). What mass of water evaporates?
A:O 150 g
B:O 22 g
C:11,962 g
D:O 105,000 g

Explanation:

We need to use the formula for heat of vaporization.

Identify the variables.

Substitute the values into the formula.

We want to find the mass. We must isolate the variable, m.

m is being multiplied by 2260 J/g. The inverse operation of multiplication is division. Divide both sides by 2260 J/g.

Divide. Note that the Joules (J) will cancel each other out.

Round to the nearest whole number. The 1 in the tenth place tells us to leave the number as is.

The mass is about 22 grams, so choice B is correct.

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.