As with most questions that pertain to human anatomy there is a lot of natural variation. The normal human stomach has a pH which can range from approximately 1-3 but is usually closer to 2. When there is food in the stomach the pH can raise to as high as 4-5. After the food leaves the stomach bicarbonate ions are secreted to neutralize and alkalinize the mixture. The pH of the small intestine is approximately 8.

As far as how long food stays in your stomach it depends on what that food is.
Some foods that contain simple carbohydrates (such as sugar or white bread) are relatively fast to digest compared to more complex carbohydrates or proteins.
Foods contain a variety of different levels of carbohydrates, fats, oils, protein, fiber, etc. all of which have different mechanisms and rates of digestion. If for example you eat some trail mix, the chocolate chips will be digested rapidly, the fruit will take longer, and the nuts could take several hours. The range in digestion times is large: if the stomach is empty water will leave immediately and go to the intestines, whereas meats such as beef and pork can take upwards of 4 hours.
Its a short answer but hope it helps...

The pH of your stomach acid is pH 1 to 3, which is a strong acid. (This is when it's empty and pH 5 when it's full.)

Meat spends 3-6 hours in the stomach, or longer if there is fat in the stomach, too. Water and alcohol are absorbed on a time scale of seconds to minutes through the mouth, stomach and digestive tract.

I learned in a nutrition class that the old picture of the stomach is a bag with all our food mixed up in it. The new view of our stomach is a bag with all our swallows of food lying one on top of each other, and the stomach digests the food and passes it to the intestine, starting at the outside layer of food. Scientists discovered that by doing some sort of experiments where people ate food that could be seen with x-rays or some sort of imaging system.

Stomach acid pH ranges between about 1 and 2. Although it can vary depending on what you choose to consume, food typically spends about 4 hours in the stomach before it reaches the appropriate consistency and enters the intestine