Answer: There are
atoms of hydrogen are present in 40g of urea,
.
Explanation:
Given: Mass of urea = 40 g
Number of moles is the mass of substance divided by its molar mass.
First, moles of urea (molar mass = 60 g/mol) are calculated as follows.

According to the mole concept, 1 mole of every substance contains
atoms.
So, the number of atoms present in 0.67 moles are as follows.

In a molecule of urea there are 4 hydrogen atoms. Hence, number of hydrogen atoms present in 40 g of urea is as follows.

Thus, we can conclude that there are
atoms of hydrogen are present in 40g of urea,
.
Answer:
(A) melting point, freezing point.
Explanation:
For the same substance: when matter is transitioning from solid to liquid <em>(melting)</em> or liquid to solid <em>(freezing)</em>, <em><u>its temperature is fixed at the melting/freezing point, which is the same temperature.</u></em>
Answer:
D. period is reciprocal of frequency.
Explanation:
Answer:

Explanation:
Force can be found by multiplying the mass and the acceleration.

The mass of the sled is 300 kilograms and the acceleration is 2 meters per second squared.

Multiply.

1 kilogram-meter per second squared is equal to 1 Newton. Therefore, 600 kilograms-meter per second squared is equal to 600 Newtons.

The force used on the sled is 600 Newtons.