Question

You mix solution A with solution B in a beaker. Which of the following observations does not help you prove that a chemical reaction has occurred?

A The beaker becomes warm.
B You see gas bubble out of solution.
C Solution A, solution B, and the mixture are all yellow.
D None of the above; all help prove that a chemical reaction has occurred.

In the reaction described by the word equation sodium + water sodium hydroxide + hydrogen gas

A sodium hydroxide is a product.
B sodium is a product.
C Both (a) and (c)
D water is a reactant.

Answer 1

1) Solution A, solution B, and the mixture are all yellow.

2) sodium hydroxide is a product

water is a reactant.

Step-by-step explanation:

In a chemical reaction mixture , change in colour, change in temperature of reaction mixture or evolution of gas all confirm that a chemical reaction has taken place. If the colour of the reaction mixture remains the same overtime, it may be an indication that a chemical reaction did not take place in the mixture.

Looking at the reaction equation:

sodium + water----------> sodium hydroxide + hydrogen gas

Species on the lefthand side of any chemical reaction equation are called reactants while the species on the right hand side of the reaction equation are called products . hence sodium hydroxide is a product while water is a reactant.

Answer 2

Part 1: A and B; Part 2: A and D

Step-by-step explanation:

Part 1. Evidence of reaction

The evolution of heat and/or bubbles of gas are evidence that a reaction has occurred.

C is wrong. If adding yellow Solution A to yellow Solution B gives a yellow mixture, that is not evidence of reaction. You need a colour change to provide evidence.

Part 2. Identifying reactants and products

`\underbrace{\hbox{sodium + water }}_{\hbox{reactants}} \longrightarrow \, \underbrace{\hbox{ sodium hydroxide + hydrogen gas}}_{\hbox{products}}`

Reactants are on the left side of the reaction arrow, and products are on the right.

Thus, water is a reactant, and sodium hydroxide is a product.

B is wrong. Sodium is a reactant.