Is .1M NaH2PO4 a good buffer? Explain.
Cu(s) + 4HNO3(aq) → Cu(NO3)2(aq) + 2H2O(l) + 2NO2(g)
i need the chemical equation and the net ionic equation
A chemist decomposes several samples of water into hydrogen and oxygen and weighs (or more correctly “measures the mass of”) the hydrogen and the oxygen obtained.
To determine whether .1M NaH2PO4 is a good buffer, we need to consider a few factors. A buffer is a solution that resists changes in pH when small amounts of acid or base are added to it. It consists of a weak acid and its conjugate base (or a weak base and its conjugate acid) in roughly equal concentrations.
In the case of NaH2PO4, it is a salt of phosphoric acid (H3PO4) and its conjugate base (H2PO4-). The dissociation of NaH2PO4 in water can be represented as follows:
NaH2PO4 → Na+ + H2PO4-
The H2PO4- ion acts as a weak acid, while the Na+ ion is a spectator ion and does not participate in the pH adjustment. NaH2PO4 can donate H+ ions to the solution to counteract any added base, thus helping to maintain pH stability.
To evaluate the buffering capacity of .1M NaH2PO4, we can consider its pKa value. The pKa is a measure of the strength of the weak acid (H2PO4-) in the buffer system. The lower the pKa, the stronger the acid and the better the buffer capacity.
The pKa value of H2PO4- is around 7.2. This means that at pH 7.2, the concentration of H2PO4- and HPO4^2- (the conjugate base) will be roughly equal in the solution.
If the desired pH of the buffer is close to the pKa value, the buffer will be most effective. In this case, since the pKa of H2PO4- is around 7.2, .1M NaH2PO4 would be a good buffer for maintaining a pH around 7.2.
However, it is important to note that the effectiveness of a buffer also depends on the ratio of the concentrations of the weak acid and its conjugate base. The optimal ratio is usually 10:1 (or 1:10), which provides the highest buffering capacity. So, for a .1M NaH2PO4 buffer to be more efficient, the concentration of H2PO4- should be around 0.09M, and the concentration of Na2HPO4 (the conjugate base) should be around 0.01M.
To prepare such a buffer, NaH2PO4 and Na2HPO4 can be weighed out in appropriate amounts, dissolved in water, and adjusted to the desired pH by adding small amounts of acid or base as needed.
In summary, .1M NaH2PO4 can be a good buffer depending on the desired pH range and the specific application. However, to maximize its buffering capacity, the pH should be close to the pKa of H2PO4-, and the concentrations of H2PO4- and its conjugate base should be optimized at a 10:1 ratio.