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# Tutor profile: Alicia G.

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Alicia G.
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## Questions

### Subject:Chemistry

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Question:

Determine the ammonium ion concentration of a solution that results when 4.53 g of (NH4)2SO4 (Molar mass = 132 g/mol) is dissolved in water and diluted to exactly 100.0 mL.

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Alicia G.

### Subject:Basic Chemistry

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Question:

How many moles are in 1.25 grams of sodium chloride, NaCl?

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Alicia G.

### Subject:Algebra

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Question:

Given the following two equations, report the values of x and y. 3x + y = 15; x + 2y = 10.

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Alicia G.

Solving two equations with two unknowns is a common type of problem which can be solved by the method of substitution: solve one equation for one variable, then insert the solution into the other equation to solve for that variable. Once the value for the first variable is known, that value can be plugged into either equation to find the value for the other variable. Remember a primary rule of algebra: whatever you do to one side of the equation, you must do to the other side. For the above problem, we could solve the first equation for y as follows: subtract 3x from both sides, to get y = 15 - 3x. Next, substitute this expression (15-3x) into the second equation in place of y: x + 2(15-3x) = 10. This equation has only one variable - x - so we can find the value for x. First, distribute the 2 over the parentheses: x + 30 - 6x = 10. Combine like terms: -5x + 30 = 10. Subtract 30 from both sides to get -5x = -20. Divide both sides by -5 to find out that x = 4. Now, plug this value of x into either of the equations to find the value of y. Plugging into the first equation, you get 3(4) + y = 15 which simplifies to 12 + y = 15. Subtract 12 from both sides to get y = 3. It's always a good idea to double-check your answer. You can plug the values of x and y that you have found into either equation to make sure you get a true statement. For example, plugging x = 4 and y = 3 into x + 2y = 10 gives 4 + 2(3) = 10, which is a true statement. Therefore, the solution is correct.

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