Question

1. the hydrogen released by the reaction of 90 grams of nitric acid on aluminum, was used to make ammonia. How many grams of ammonia were formed ? 3. How many grams of copper(II) oxide can be formed by the oxygen liberated when 150 grams of mercuric oxide are ddecomposed? 4. the iodine formed when 20 grams of chromic iodide are electrolyzed is reacted with sodium . how many moles of sodium iodide are formed? 5. A sample MgO was first dissolved in hydrochloric acid to give a solution of MgCl2 and was then converted to a precipitate of pure, dry Mg2P2O7 weighting 12.00g. calculate the sample of MgO.

Answer 1

2Al +    6HNO3 ------>2 Al(NO3)3 + 3H2

2 moles       6 moles                                      3 moles

6 moles of HNO3 react Al to from 3 moles of H2

6*63 gm HNO3 react with Al to from 3*2 gm of H2

90 gm of HNO3 react with Al to from 6 *90/378 = 1.43 gm of H2

N2 + 3H2 -----> 3NH3

2 moles of H2 react with N2 to from 3 moles of NH3

2*2gm of H2 react with N2 to from 3*17 gm of NH3

1.43 gm of H2 react with N2 to from = 51*1.43/4 = 18.23gm of NH3

3.

2HgO -----> 2Hg + O2

2 moles of HgO decomposes togives 1 mole of O2

2*216.6 gm of HgO decomposes to gives 32 gm of O2

150 gm of HgO decomposes to gives = 32*150/2*216.6 = 11.08gm of O2

2Cu + O2 ----> 2CUO

1 mole of O2 react with Cu to from 2 moles of CuO

32 gm of O2 react with Cu to from 2*79.5gm of CuO

11.08 gm of O2 react with Cu to from = 2*79.5*11.08/32 = 55.053 gm of CuO

4.

2CrI3 -----> 2Cr⁺³ + 3I2

2 moles of CrI3 gives 3 moles of I2

2*158.3 gm of CrI3 gives 3 *253.8 gm of I2

20 gm of CrI3 gives = 3*253.8*20/2*158.3 = 48.09 gm of I2

2Na + I2 ----> 2NaI

1 mole of I2 react with Na to from 2 moles of NaI

158.3 gm of I2 react with Na to from 2*150 gm of NaI

48.09gm of I2 react with Na to from = 2*150*48.09/158.3 = 91.13 gm of NaI

no of moles of NaI = 91.13/150 = 0.6 moles of NaI