Heptane: C₇H₁₆. Combustion is when a molecule reacts with O₂ and the products are CO₂ and H₂O. Balancing gives 7 CO₂, 8 H₂O, 1 heptane, and 11 O₂

The longer the hydrocarbon chain, the greater the amount of combustion products (CO2 and H20) generated. Branched molecules such as isopropane and isobutane are more difficult to combust than their straight-chain counterparts.

An exothermic reaction will have a negative  value, indicating that it releases heat. Conversely, an endothermic reaction will have a positive  value, indicating a consumption of heat.

A combustion reaction releases heat; thus it must have a negative  value and be exothermic.

Exergonic reactions have a negative  value, indicating spontaneity, while endergonic reactions are non-spontaneous. While most combustion reactions will be non-spontaneous, it is impossible to draw this conclusion for certain without knowing more about the reaction. The only thing we know for certain is that heat is released, and the reaction is exothermic.

pOH would be 4 (use –log [OH–]) and pH would be 14–pOH = 14 – 4 = 10

[OH^-] = 4 X 10^-6

pOH = 5.4 — use –log [OH^–] to find pOH

pH = 14– pOH = 8.6

The pH of a solution is determined by taking the negative log of the concentration of hydrogen ions in solution.  HCl is strong acid so it completely dissociates in solution.  So adding .0001 M HCl is the same as saying that 1 *10^-4 moles of H+ ions have been added to solution.  The -log[.0001] =4, so the pH of the solution =4.  

This question asks for the solution with the greatest number H⁺ ions, we can also approach this problem as if we are looking for the solution with the lowest pH. HCl is strong acid, therefore it will dissociate completely in solution. So the solution containing 0.010 mL of HCL contains 0.010 mL of H⁺ ions in solution, in addition to the H⁺ ions that are already in solution due to the auto-ionization of water. The only other solution that could have a pH less than 7 would be the one with 0.010 mL of CH₃OH in excess water, becasue CH₃OH is very slightly acidic.  But since it is compared with an equal volume of HCl which is strong acid, it can be said that the most H⁺ ions will be found in the solution containing a small amount of strong acid, HCl.  

Calcium carbonate is a base since it's the salt of a strong base (NaOH) and a weak acid (carbonic acid). The only basic pH on the list is 8, making it the correct answer. 

The –log of the pKa will give you the Ka, so take the –log (6.4), which gives you approximately 4 * 10^–7. The Ka expression is set up with products over reactants (hydrogen carbonate ion * hydrogen ion/carbonic acid). The undissociated carbonic acid is 0.001M, and you should use the variable 'x' to account for how much it dissociates and how many of the ions are produced. Ka = 4 * 10^–7 = x²/0.001 ends up being your Ka expression, if you assume x is negligible compared to the original concentration of 0.001. Solving for x, you get 2 * 10^–5. This is the hydrogen ion concentration. pH = –log (hydrogen ion concentration), so pH = –long(2 * 10^–5), which is approximately 4.7.

For a solution to be acidic, it must have a pH between 1 and 6.99, since 7 is neutral; pH is –log(hydrogen ion concentration), the range of possible values is between 10^–1 and 10^–6.999.