Question

Question 19
One molecule of Iodine (I2) and two molecules of sodium chloride (NaCl) combine in a reaction. How many atoms are in the products?

a
3
b
2
c
4
d
6
Question 20
Which event is an example of an exothermic reaction?

a
combustion
b
melting ice
c
evaporation
d
decomposition

Answer 1

**Question 19:** To determine the number of atoms in the products of the reaction between one molecule of iodine (I₂) and two molecules of sodium chloride (NaCl), we first need to analyze the components involved.

- I₂ consists of 2 iodine atoms.
- Each NaCl consists of 1 sodium atom and 1 chlorine atom. Therefore, 2 molecules of NaCl consist of:
- 2 sodium atoms
- 2 chlorine atoms

Adding these together:
- From I₂: 2 iodine atoms
- From 2 NaCl: 2 sodium atoms + 2 chlorine atoms = 4 atoms

Total number of atoms = 2 (I) + 2 (Na) + 2 (Cl) = 6 atoms.

So, the answer is **d) 6**.

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**Question 20:** An exothermic reaction is a chemical reaction that releases energy, often in the form of heat. Among the options given:

- a) **Combustion** - This is a typical example of an exothermic reaction, as it releases a significant amount of energy.
- b) Melting ice - This is an endothermic process since it requires energy to change from solid to liquid.
- c) Evaporation - This is also an endothermic process, as it requires energy to convert liquid to gas.
- d) Decomposition - This can be endothermic or exothermic, depending on the specific substances involved.

Therefore, the best answer for an example of an exothermic reaction is **a) combustion**.