What is the effect on molarity for NaOH when balance used to weigh KHP is not properly calibrated and always reads 0.15 g too low.
To determine the effect on molarity for NaOH when the balance used to weigh KHP (potassium hydrogen phthalate) is not properly calibrated and always reads 0.15 g too low, we need to understand the process involved.
1. Start by recalling the equation for the reaction between NaOH and KHP:
NaOH + KHP → NaKP + H2O
2. The balanced equation tells us that one mole of NaOH reacts with one mole of KHP.
3. The molarity of NaOH (M) is defined as the number of moles of NaOH per liter of solution.
Now, let's consider the effect of the improperly calibrated balance:
a) If the balance weighs KHP as 0.15 g too low, it means that the measured mass will always be underestimated. This leads to a smaller amount of KHP being used in the reaction.
b) Since the reaction between NaOH and KHP is a stoichiometric one-to-one reaction, a smaller amount of KHP will correspond to a smaller amount of NaOH required to react completely.
c) As a result, the calculated molarity of NaOH will be higher than the actual molarity. This is because the molarity is calculated based on the measured mass of KHP and the volume of NaOH used.
To find the actual molarity, you can use the following steps:
1. Record the measured mass of KHP from the improperly calibrated balance.
2. Since the balance consistently reads 0.15 g too low, adjust the measured mass by adding 0.15 g to obtain the correct mass of KHP.
3. Use the correct mass of KHP along with the volume of NaOH used in the reaction to calculate the moles of KHP.
4. Since the reaction is one-to-one, the moles of KHP will be equal to the moles of NaOH used.
5. Divide the moles of NaOH by the volume of NaOH used (in liters) to determine the actual molarity of NaOH.