Answer:
C
Explanation:
the respiratory system and the circulatory system work closely together to deliver oxygen to cells and to get rid of the carbon dioxide the cells produce. The circulatory system picks up oxygen in the lungs and drops it off in the tissues, then performs the reverse service for carbon dioxide.
Answer:
Explanation:
You just have to see the REACTANTS and PRODUCTS and look how much molecules are there and accordingly put numbers.
Eg:4Fe+3O2--------->2Fe2O3
Answer:
1. pH = 1.23.
2. 
Explanation:
Hello!
1. In this case, for the ionization of H2C2O4, we can write:

It means, that if it is forming a buffer solution with its conjugate base in the form of KHC2O4, we can compute the pH based on the Henderson-Hasselbach equation:
![pH=pKa+log(\frac{[base]}{[acid]} )](https://tex.z-dn.net/?f=pH%3DpKa%2Blog%28%5Cfrac%7B%5Bbase%5D%7D%7B%5Bacid%5D%7D%20%29)
Whereas the pKa is:

The concentration of the base is 0.347 M and the concentration of the acid is 0.347 M as well, as seen on the statement; thus, the pH is:

2. Now, since the addition of KOH directly consumes 0.070 moles of acid, we can compute the remaining moles as follows:

It means that the acid remains in excess yet more base is yielded due to the effect of the OH ions provided by the KOH; therefore, the undergone chemical reaction is:

Which is also shown in net ionic notation.
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Answer:
K^+ and NO3^-
Explanation:
In a balanced ionic equation, we usually see the species that react to yield the main product in the reaction.
Consider the reaction;
Pb(NO3)2(aq) +2 KI(aq) -------> PbI2(s) + 2KNO3(aq)
The main product in this reaction is PbI2. Hence the balanced ionic equation is;
Pb^2+(aq) + 2I^-(aq) ------> PbI2(s)
Notice that K^+ and NO3^- did not participate in this reaction. All ions that are part of the molecular equation but do not participate in the ionic reaction equation are called spectator ions. Hence K^+ and NO3^- are spectator ions in this reaction as can be seen clearly above.