Hi, what is the PH for NH3 in gas form? When I tested it with PH paper it showed a number around 8-9.5, but from searching online its a higher number. I'm not sure which one is correct. Thanks
Ammonia in the gas form has no pH. Only when it is dissoved in water (or water vapor), does it exhibit pH. If you tested it with dry pH paper, in the pure gas form (no water vapor), you would have gotten no reaction.
Hi, I tested it with moist PH paper, i think its from the water vapour, what PH was i suppose to get?
How much water? How much gas? Do you have any way of knowing the concentration of the NH3(aq) that was on the paper? Probably not. Whatever pH you obtained is the pH you should get if the paper was the right kind of pH paper.
The pH of NH3 (ammonia) in gas form is actually higher than what you observed with pH paper. Ammonia is a weak base, which means it tends to accept protons (H+) in a chemical reaction. pH is a logarithmic scale that measures the concentration of H+ ions in a solution, with lower numbers indicating higher acidity and higher numbers indicating higher alkalinity or basicity.
To accurately determine the pH of NH3 gas, you will need to use a different method. pH paper is typically designed to measure the pH of liquids and may not be as accurate for gases. Online sources will provide more accurate information.
One way to determine the pH of NH3 gas is to dissolve it in water to form an aqueous solution. The dissolved NH3 gas reacts with water to form ammonium hydroxide (NH4OH):
NH3(g) + H2O(l) ⇌ NH4OH(aq)
The pH of the resulting ammonium hydroxide solution can be measured using a pH meter or pH indicator solutions specifically formulated for aqueous solutions.
Alternatively, you can calculate the pH of NH3 gas using the pKa value of its conjugate acid, NH4+. The pKa value represents the strength of an acid, and in this case, it indicates how much NH4+ ions dissociate in water. The pKa value for NH4+ is around 9.25, which indicates that only a small fraction of NH4+ ions will dissociate into H+ ions and NH3 gas.
To calculate the pH, you can use the formula:
pH = pKa + log ([A-]/[HA])
In this case, [A-] represents the concentration of NH4+ (which is relatively small), and [HA] represents the concentration of NH3 gas. Plugging in the values, the pH is expected to be higher than 9.25.
Therefore, based on this information, the online sources are likely more accurate, and the pH of NH3 gas is higher than the pH paper reading of 8-9.5.