# Tutor profile: Karin C.

## Questions

### Subject: Chemistry

What are the numbers around a chemical symbol on the periodic table?

The number above the chemical symbol is the atomic number. Each element has a different atomic number. For example, hydrogen has the atomic number 1, helium has the atomic number 2, and so on. Atomic numbers are sometimes symbolized with a Z. The atomic number tells you how many protons and, in an uncharged atom, electrons an element has. The number below the chemical symbol is the mass number (symbolized A), and it tells you the atomic weight of an element in amu. The mass number corresponds to the molarity of a substance (for instance, hydrogen has a molarity of about 1.008 g/mol), and it can be used to determine the number of neutrons. Helium's atomic number is 2, meaning that it has 2 protons. It's mass number is just over 4, which means that it has 2 protons and 2 neutrons.

### Subject: Calculus

What is the derivative of f(x)=(x^3-2)/(4x) ?

There are, as always with math, several ways to solve this. One way is to use the quotient rule and then the power rule. The quotient rule states that the derivative of a fraction is equal to the numerator multiplied by the derivative of the denominator, subtracted from the denominator multiplied by the derivative of the numerator, all set over the denominator squared (f/g)'(x) = [g(x)*f'(x) - f(x)*g'(x)] / [g(x)^2]. To do this, we would find the derivative of the numerator and denominator individually (3x^2 and 4, respectively, from the power rule), and then plug those into our statement from earlier. Thus f'(x) = [(4x*3x^2) - ((x^3-2)*4)]/(4x)^2 , which simplifies to f'(x) = (12x^3 - 4x^3 - 8) / (16x^2) .

### Subject: English

What's the difference between affect and effect?

Affect is the Action; Effect is the End result.

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