Question 15 and 16 plss

Question 15 and 16 plss 8. Determine the percentage composition of potassium nitrate (KN03) Atomic masses K = 39, 9. Sugar (Ct2H22011) costs Rs. 15 per Kg How much one mole sugar would cost? 10. Calculate the number of water molecules present in a spherical drop of water having a radi Of 1 mm. Take density Of water as 1 g/cc. 11. A substance on analysis gave the following percentage composition Na = 43.4% C = 11.3% and O 45.3%. Determine the empirical formula and molecular formula. Given molecular mass is 1 ()6. 12.A compound was found to have 78.2% boron and 21.8% of H. Its molecular mass was determined to be 27.6 g/mole. What is the molecular formula of the compound? Atomic masses of Boron = 11 and Hydrogen = 1 13. Write the empirical formula of the compounds having molecular formulae (1) C6H6 (2) C6H12 (3) H202 (4) H20 (5) NazC03 (6) B2H6 (7) N204 (8) H3P04 (9) (10) 14.2 atoms Of hydrogen combine With I atom Of oxygen to give one molecule ofwater. HOW many hydrogen is needed to react completely with 6.4 g of oxygen gas? 15. When zinc sulphide (ZnS) is strongly heated in excess of air, zinc oxide (ZnO) is formed gaseous S02 is evolved. Calculate the mass Of ZnO and S02 that can be obtained from 4.866 of zns. 16. What mass of Na is required to produce 34.0 of NH3 by the reaction N2+3H2 2NH3 17. Methane burns in oxygen to form carbon di oxide and water. Write the balance chemical equation for this reaction. From this reaction calculate the oxygen required for burning 1.6 ofmethane (C 12 0 = 16&H 1) 18. What mass of copper oxide will be obtained by heating 12.35 g of copper carbonate? Atomi mass Of copper is 63.5 g/mole. 19. Copper wire reacts with silver nitrate (AgN03) solution to give silver metal (Ag) and a solution of copper nitrate How many gram of metallic silver is produced if 2.37 g Of copper has reacted? 20. Hydrazine (N2H4) and hydrogen peroxide (H204) are used together as rocket fuel. The products of the reaction are nitrogen and water. How many grams of H202 are needed per I of hydrazine carried by rocket? 21. Find the percentage purity of NaCl 6.5 g ofwhich when dissolved in water and treated silver nitrate solution gave 14.35 g of silver chloride. 22.2.3 g of metallic sodium reacts with excess of water. Calculate the mass of sodium h formed. What is the volume of hydrogen evolved at NTP. 23. Calculate the volume of oxygen gas evolved at STP by decomposing 12.26 gm of KC103. 24. What volume of carbon dioxide is formed under STP condition by complete combustion of I Kg Of carbon in an excess Of oxygen? 25. What volume of air containing 21% of oxygen (by vol) is required to completely burn 10 g sulphur which has a purity level of 98%? 26. A small piece Of commercial Zinc weighing I O g is made to react With excess Of dilute sulphuric acid. The total volume of hydrogen gas liberated was found to be 3.1 litre at NTP, Determine the percentage purity Of the zinc sample. 27. A sample Of NaOH weighing 0.38 g is dissolved in water and the solution is made to 50 ml i volumetric flask. What is the molarity of the resulting solution?

Answer 15:

The reaction is as follows:

2 ZnS(s) + 3 O₂(g)

\to

2 ZnO + 2 SO₂

we see that 2 moles of ZnS gives 2 moles of ZnO and 2 moles of SO₂. So,

Number of moles of ZnS =

\frac{G i v e n m a s s}{m o l a r m a s s} = \frac{4.866}{97.474} = 0.0499 m o l e s

Mass of ZnO = 81.408

\times

0.0499 = 4.045 g
Mass of SO₂ = 64.06

\times

0.0499 = 3.19 g.

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