Check my answers for 2 questions? The one I think is correct is marked by a ***.
4. Which of the following mixtures is NOT an example of a substance?
drinking water
air***
brass
pizza

5. A solution with a pH of 13 is a ____.
weak acid***
weak base
strong acid
strong base

Question

Check my answers for 2 questions? The one I think is correct is marked by a ***.
4.   Which of the following mixtures is NOT an example of a substance?  
drinking water
air***
brass
pizza

5.   A solution with a pH of 13 is a ____.  
weak acid***
weak base
strong acid
strong base

anonymous · Answer

correct :)

blues · Answer

Hmm, with respect to the first question I think the item which is not a substance is pizza.

And with respect to the second, acids have pHs of less than seven while bases have pHs of more than seven. As the pH scale ranges from 0 to 14 and as 13 is very close to one end, I think it's a strong whatever it is too.

anonymous · Answer

Also, THANK YOU for putting what you thought the answer was!  That's very helpful for the people replying. (I don't have anything to add beyond what @blues said as to the content of your question, just wanted to comment on the form.).

anonymous · Answer

a solution with a pH of 13 is a (very!) strong base. i mean, even when you work with strong bases in chemistry labs that's a very high pH.
about the first question: none of the options is chemically a substance, for all of them are mixtures, as the question itself states.

blues · Answer

Homogenous mixtures are chemically substances. The first question asks the person to distinguish between macroscopically homogeneous mixtures and the one on the list which plainly isn't...

anonymous · Answer

ok, i thought the question meant "substance" as a defined "formula"...for example, "drinking water" is not just H2O but also salts, carbon dioxide, etc.
but that's fine, it's a matter of definition.

blues · Answer

It is a matter of semantics and how you interpret words, which is why I tend to avoid questions like this if possible. Well spotted, though. :D

anonymous · Answer

i just joined this site, i'm "exploring" what kind of questions there are. i'll try to be less naïve, lol :D besides, spanish is my first language, so i was kind of surprised, thinking that "substance" was something different from "sustancia" in spanish.....

blues · Answer

Welcome to OpenStudy! The questions range in difficulty, from simple to graduate and professional level. It's not hard - you will learn quickly. We do have one or two other Spanish speakers in the biology group...

anonymous · Answer

well thank you! we'll keep in touch then. i'm also in the math and spanish groups (in math i've got more questions than answers certainly).