Qui 3 & 4

1.     Which law states that the total mass of products of a chemical reaction is equal to the total mass of reactants.

• Law of constant composition

• Law of multiple proportions

• Law of conservation of mass      

• None of the above

2.     In the following diagram, the white spheres represent hydrogen atoms and the blue represent nitrogen atoms. How many atoms of NH₃ molecules should be in the right (products) box?

3. Calculate the percentage by mass of the indicated element in the following compounds:

a.      Percentage of oxygen in cocaine- C₁₇H₂₁NO₄

4.     Calculate the percentage by mass of the indicated element in the following compounds:

Percentage of platinum in Cisplatin – PtCl₂(NH₃)₂

5.  How many moles of sodium bicarbonate (NaHCO₃) are present in 508g of NaHCO₃?

6.    A compound whose empirical formula is XF₃ contains 65% F by mass. What is the atomic mass of X?

7.     A compound consists of Carbon, Hydrogen and Oxygen. 8.272g of CO₂ and 4.515g H₂O are produced during complete combustion of 3.765g of the compound.

What is the empirical formula of the compound?

b.      What is the molecular formula if the molar mass of the compound is 300.47g/mol ?

8.     Decomposition of KClO₃ is used to prepare small amounts of O₂ in the laboratory. KClO₃(s) → KCl (s) + O₂(g)

a.      How many grams of O₂ can be produced from 4.50g of KClO₃?

9.     How many moles of HCl are present in 35.0 mL of a 4.50 M solution of nitric acid?