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3 years ago

6

13. Which statement about trace elements in our atmosphere is false?

1 answer:

tatiyna3 years ago

6 0

Answer: sorry I’m not sure

Odjri:

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Cooking an egg is an example of what type of change

Katen [24]

Answer: chemical change

7 0

2 years ago

What percentage of the mass of hydrofluoric acid (HF) is contributed by hydrogen?

Morgarella [4.7K]

This problem is asking for the percent by mass of hydrogen in hydrofluoric acid. At the end, the answer turns out to be D. 5% as shown below:

<h3>Percent compositions:</h3>

In chemistry, percent compositions are used for us to know the relative amount of a specific element in a compound. In order to do so for hydrogen, we use the following formula, which can also be applied to any other element in a given compound:

$\% H=\frac{m_H*1}{M_{HF}}*100\%$

Where $m_H$ stands for the atomic mass of hydrogen and $M_{HF}$ for the molar mass of hydrofluoric acid. In such a way, we plug in the atomic masses of hydrogen (1.01 g/mol) and fluorine (19.0 g/mol) to obtain:

$\% H=\frac{1.01g/mol*1}{1.01g/mol+19.0g/mol}*100\%\\\\\% H=5\%$

Learn more about percent compositions: brainly.com/question/12247957

5 0

2 years ago

What is the most common isotope for element X

ankoles [38]

Answer:

isotope 2

Explanation:

it has the highest percentage abundance

5 0

2 years ago

I bet no one can solve this

Nikitich [7]

The answer is 89.4 g/mol cuz the two units carry positives so that means 8.50 flows for 2 more hours than usual.

3 0

3 years ago

How many grams of solid NaOH are required to prepare a 400ml of a 5N solution? show your work!

Nuetrik [128]

<u>Answer:</u> The mass of solid NaOH required is 80 g

<u>Explanation:</u>

Equivalent weight is calculated by dividing the molecular weight by n factor. The equation used is:

$\text{Equivalent weight}=\frac{\text{Molecular weight}}{n}$

where,

n = acidity for bases = 1 (For NaOH)

Molar mass of NaOH = 40 g/mol

Putting values in above equation, we get:

$\text{Equivalent weight}=\frac{40g/mol}{1eq/mol}=40g/eq$

Normality is defined as the umber of gram equivalents dissolved per liter of the solution.

Mathematically,

$\text{Normality of solution}=\frac{\text{Number of gram equivalents} \times 1000}{\text{Volume of solution (in mL)}}$

Or,

$\text{Normality of solution}=\frac{\text{Given mass}\times 1000}{\text{Equivalent mass}\times \text{Volume of solution (in mL)}}$ ......(1)

We are given:

Given mass of NaOH = ?

Equivalent mass of NaOH = 40 g/eq

Volume of solution = 400 mL

Normality of solution = 5 eq/L

Putting values in equation 1, we get:

$5eq/L=\frac{\text{Mass of NaOH}\times 1000}{40g/eq\times 400mL}\\\\\text{Mass of NaOH}=80g$

Hence, the mass of solid NaOH required is 80 g

4 0

3 years ago