A solution containing 1.20 g of impure sodium hydroxide solution per Liter. In a titration, it requires 18.5 L of 0.500 mol/ L of sulfuric acid to neutralize 20.0 L of the impure alkaline solution completely. The chemical reaction is shown below. 2NaOH + H2SO4 Na2SO4 + 2H2O

Determine the concentration of NaOH in mol/L

answer: c. the experiment shows that the red substance experienced a chemical change.

explanation: chemical change is the change in which chemical composition of the substance changes. physical change is the change in which there is no change in chemical composition.

chemical changes are accompanied by following changes:

a) precipitate formation

b) energy is released or absorbed

c) formation of bubbles

d) change in color

as it is given that the red color has disappeared and there is production of gas, it means the red substance has undergone a chemical change.

e

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.