If a helium balloon has a volume of 8.5 L assuming STP conditions, how many moles are there?

answer

0.37946 moles

explanation

at STP, there are 22.4 liters for every mole of gas, so divide the number of liters by 22.4 to find the number of moles

number of moles =

number of moles = 0.37946 moles

the correct answer is a

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.