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Alecsey [184]
3 years ago
11

A hydrate is compound that included water molecules within its crystal structure. During an experiment to determine the percent

by mass of water in a hydrate crystal, a student found the mass of the hydrated crystal to be 6.235g. After heating to constant mass, the mass was 4.90g. What is the percent by mass of water in this crystal? *
22%
21.4%
78.5%
27%
Chemistry
2 answers:
Gnoma [55]3 years ago
7 0

Question:

Options available;

a. 22%

b. 21.4%

c. 78.5%

d. 27%

Answer:

The percentage by mass of water in the crystal is 21.4%

The correct option is;

b. 21.4%

Explanation:

From the question,

The initial mass of hydrate crystal = 6.235 g

Final mass of crystal = 4.90 g

Mass of water molecules displaced = 6.235 g - 4.90 g = g

Percentage by mass of water in the crystal is found from the following relationship;

1.335

Therefore;

Percentage \ by \ mass = \frac{1.335 \ g}{6.235 \ g} \times 100= 21.41  \% \approx 21.4\%

The percentage by mass of water in the crystal = 21.4%.

stellarik [79]3 years ago
4 0

Answer:

The percent by mass of water in this crystal is:

  • <u>21.4%</u>

Explanation:

This exercise can be easily solved using a simple rule of three where the initial weight of the hydrated crystal (6,235 g) is taken into account as 100% of the mass, and the percentage to which the mass of 4.90 g corresponds (after getting warm). First, the values and unknown variable are established:

  • 6,235 g = 100%
  • 4.90 g = X

And the value of the variable X is found:

  • X = (4.90 g * 100%) / 6,235 g
  • X = approximately 78.6%.

The calculated value is not yet the percentage of the water, since the water after heating the glass has evaporated, therefore, the remaining percentage must be taken, which can be calculated by subtraction:

  • Water percentage = Total percentage - Percentage after heating.
  • <u>Water percentage = 100% - 78.6% = 21.4%</u>
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3 0
3 years ago
The titration of 78.5 mL of an unknown concentration H3PO4 solution requires 134 mL of 0.224 M KOH solution. What is the concent
Katyanochek1 [597]

Answer:

0.127 M.

Explanation:

The balanced equation for the reaction is given below:

H3PO4 + 3KOH —› K3PO4 + 3H2O

From the balanced equation above, we obtained the following data:

Mole ratio of acid, H3PO4 (nA) = 1

Mole ratio of base, KOH (nB) = 3

Data obtained from the question include:

Volume of acid, H3PO4 (Va) = 78.5 mL

Molarity of acid, H3PO4 (Ma) =...?

Volume of base, KOH (Vb) = 134 mL

Molarity of base, KOH (Mb) = 0.224 M

The concentration of the acid, H3PO4 can be obtained as follow:

MaVa / MbVb = nA/nB

Ma x 78.5 / 0.224 x 134 = 1/3

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Ma x 78.5 x 3 = 0.224 x 134 x 1

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Ma = 0.127 M

Therefore, the concentration of the acid, H3PO4 is 0.127 M.

3 0
3 years ago
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