Question

5. How many atoms of nitrogen are in 10 grams of NHINO? a)0.125 b) 2 17.53 x 10 d) 1.51 x 10 1 6.02 x 10 6. The average molar mass of Cu, which has two naturally cecurring isotopes is of the islopes has an atomic weight of 619 amu and makes up e9.1% of lhe custope. The other isotope has an abundance of 30.9% . The atomic weight (am) of the second istice is 63.5 amu. One a 63.2 b) 63.8 el 64.1 d) 64.8 e) 28.1 7. Under special conditions, nitrogen and hydrogen undergo a combination reaction to yield ammonia: If the reaction yield is 8 1.4%. how many moles of N2 are needed to produce 850 moles of NH? a) 20.9 b) 10.4 c) 5.22 d) 6.92 e) 15.7 8. Wha is the smallest amount of oxygen gas? (a) 16 grams (b) 16 moles (e) All the same (c) 16 molecules (d) 1 mole

Answer 1

5)

Molecular weight of NH₄NO₂ 64.06 g/mol

Moles of NH₄NO₃ = 10 g /80 g/mol == 0.125 moles

So, moles of nitrogen = 2 x 0.125 = 0.250 moles

1 mole contain 6.022 x 10²³ atoms

0.312 moles contain = 0.250 x 6.022 x 10²³ atoms == 1.51 x 10²³ atoms

(6)

given average value = 63.5 amu

so,

69.1 % x 62.9 amu + 30.1% x Cu = 100%x 63.5 amu

Cu = 63500-(69.1 % x 62.9 amu ) / 30.1

= 64.8 amu

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