# Tutor profile: Dina E.

## Questions

### Subject: Pre-Calculus

Find the exact value of sin(30).

First, you have to start by finding the angle on the unit circle. Because it's asking for "sin" that means you look at the y-axis for that angle and that's the answer.

### Subject: Basic Chemistry

When aluminum is placed in concentrated hydrochloric acid, hydrogen gas is produced. 2Al (s)+ 6HCl (aq) ---> 2AlCl3(aq) + 3H2 (aq) What volume of H2 (g) is produced when 4.90g of Al(s) reacts at STP?

For starters, separate the known and Unknown, In this case, you have 4.90g of Al(s) and need to find the volume in Liters of H2(g). The first approach would be to use the known to go to moles. Finding the moles allows you to go from one species in the equation to the next. Use 4.90g Al divide by the molar mass to convert to moles. Use that number of moles and use the coefficients to go from the number of moles of Al(s) to H2(g). After finding the number of moles of H2(g) you multiply the number of moles times 22.4L because one mole equals 22.4L. The number at the end is the volume of H2(g)

### Subject: Algebra

how to divide a fraction with different denominator?

Well, first you need to write down the first fraction as is, then flip the division sign to multiplication and flip the second fraction. multiply the numerators, as well as the denominators, then simplify (if needed).

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