# Stoichiometry

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## Stoichiometry Answer Key

1.

If [math]W_2[/math] is the weight of solute in grams or Kgs and [math]W_1[/math] is the weight of solvent in grams or kgs, then what is the concentration of such a solution in parts per million (ppm)?

- Parts per million (ppm) = [math](W_2)/(W_1 + W_2) xx 10^6 [/math]
- Parts per million (ppm) = [math][(W_1 + W_2)/W_1] xx 10^-3[/math]
- Parts per million (ppm) = [math](W_1)/(W_1+W_2) + 10^2[/math]
- parts per million (ppm) = [math](W_2)/ (W_1 -W_2) xx 10^5[/math]

2.

A sample of KCl weighing 10 g is dissolved in 200 mL of water. What is the weight percent of KCl in the solution (density of water = 1 g/mL)?

- 4.76%
- 4.53%
- 4.95%
- 4.85%

3.

Calculate the mass of sodium in kilograms present in 95 kilograms of a crude sample of sodium nitrate, whose percentage purity is 70%.

- 17.99 Kg
- 16.56 Kg
- 18.35 Kg
- 11.25 Kg

4.

What do you term the ratio of the mass of the solution to the mass of an equal volume of water at a specified temperature?

- Specific gravity
- Density
- Molarity
- Molality

5.

If W grams of solute, having an equivalent weight E, is dissolved in V liters of the solution, what is the expression of normality (N) in this case?

- [math]N = (W/E) (1/V)[/math]
- [math]N = (WE)/V[/math]
- [math]N = (WV)/E[/math]
- [math]N = (EV)/W[/math]

6.

The concentration expressed in terms of mole fraction and molality is independent of temperature.

- True
- False

7.

How many grams of NaOH are present in 1 mole of NaOH?

- 40 grams
- 50 grams
- 60 grams
- 70 grams

8.

The mole is based on

- speed of light.
- Planck's constant.
- pi.
- Avogadro's number.

9.

The sum of the mole fractions of all the components in a given solution is equal to unity.

10.

Determine the number of moles present in 0.0632 g of sulfur.

- Award credit for any one of the following answers:

• 0.002 mol

• 0.00197 mol

• 0.0020 mol

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