# Tutor profile: Vaidehi K.

## Questions

### Subject: French

Je suis très fatigué! Aujourd'hui, j'ai _____ beaucoup. A) marché B) maigri C) mangé D) mentionné

La réponse correct est A. Les quatres réponses sont dans la passé composé, mais le premier choix est quelque chose qu'un fait pour être fatigué. Marché est la passé composé de la verbe marcher. The correct choice is A. The four choices are in the past tense, but only the first choice is something that we do to be tired. The word "marché" is the past tense of the word "marcher" (to walk).

### Subject: Trigonometry

A triangle has the angles A, B, and C and sides a, b, and c. Side a is 300 meters and side c is 600 meters. Find the sine angle A.

SohCahToa is often used in trigonometry problems. The sine is equal to the opposite side/hypotenuse. The cosine is equal to the adjacent side/hypotenuse. The tangent is equal to the opposite side/adjacent side. To find the sine of A, we must find the length of the opposite side, which is 300 meters and the length of the hypotenuse, which is 600 meters. Because sine=opposite/hypotenuse, sineA=300 meters/600 meters, which is equal to .5. Therefore, sine A is .5.

### Subject: Basic Chemistry

Write and balance the following chemical equations from the word equation: In the thermite reaction, aluminum metal reacts with iron (III) oxide to form aluminum oxide and solid iron metal.

Aluminum metal is simply Al. Iron (III) oxide indicates one of the compounds in the equation will include Fe and O. The "(III)" after the iron illustrates the charge on the iron atom, which is 3. Because the oxygen has a charge of -2 and the two charges from the two atoms (Fe and O) must balance to equal zero, the compound is Fe2O3. Two atoms of iron (III) will have a charge of +6 and three atoms of oxygen will have a charge of -6. The two charges cancel out. So far we know that Al and Fe2O3 will react to form the products. The products are aluminum oxide and solid iron metal. Because aluminum has a charge of 3 and oxygen has a charge of -2, the product is Al2O3. Two aluminum atoms, each with a charge of 3, will have an overall charge of 6. Meanwhile, three oxygen atoms, each with a charge of -2, will have an overall charge of -6. Solid iron metal is Fe. The equation so far is Al + Fe2O3 --> Al2O3 + Fe. In this equation, the number of aluminum atoms and the number of iron atoms is not equal to the reagents and products. Two balance the equation, we must have an equal number of each kind of atom. On the reagents side, there is one aluminum atom, two iron atoms, and three oxygen atoms. On the products side, there are two aluminum atoms, one iron atom, and three oxygen atoms. We must increase the number of aluminum atoms on the reagents side to two and we must increase the number of iron atoms on the products side to two. By adding a 2 in front of the Al on the reagents side, we are able to increase the number of aluminum atoms to two, balancing the number of aluminum atoms for the reaction. By adding a 2 in front of the FE on the products side, we are able to increase the number of iron atoms to two, balancing the number of iron atoms for the reaction. The final balanced equation is: 2Al + Fe2O3 --> Al2O3 + 2Fe.

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