Final answer:
Approximately 1.03 x 10^25 hydrogen atoms are present in 25.6 g of urea, calculated by converting the mass to moles and then using Avogadro's number and the number of hydrogen atoms per molecule of urea.
Step-by-step explanation:
To calculate the number of hydrogen atoms present in 25.6 g of urea [(NH2)2CO], we first need to determine the number of moles of urea in the given mass. Using the molar mass of urea, 60.06 g/mol, we divide the mass of the sample by the molar mass:
Moles of urea = mass of urea / molar mass of urea = 25.6 g / 60.06 g/mol = 0.426 moles
Each molecule of urea contains 4 hydrogen atoms, as it is composed of two NH2 groups. Therefore, we can find the total number of hydrogen atoms by multiplying the number of moles of urea by Avogadro's number (6.022 x 1023 atoms/mol) and then by 4:
Hydrogen atoms = moles of urea x Avogadro's number x 4 = 0.426 moles x 6.022 x 1023 atoms/mol x 4 ≈ 1.03 x 1025 hydrogen atoms
Thus, there are approximately 1.03 x 1025 hydrogen atoms in 25.6 g of urea.