Find the mass of nitrogen supplied to soil by 5kg of urea CO(NH2)2. (O=16,N=14,C=12H=1)

2,33 kg nitrogen

Explanation:

MOLAR MASS UREA = 12 + 16 + 2*14 + 4*1 = 28 + 28 + 4 = 60 g/mole

5kg = 5000g

1 mole - 60 g

x mole - 5000 g

x = 500/6 mole

1 mole urea - 28 g nitrogen

500/6 mole - y

y = 7000/3 g ≅ 2333,33 g ≅ 2,33 kg nitrogen

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.