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3 years ago

What is the percentage by mass of oxygen in a formula unit of sodium hydrogen carbonate (NaHCO3)?

Chemistry

2 answers:

nadezda [96]3 years ago

8 0

Percent by mass of an element can be calculated as

(Total mass of the element in the formula / formula weight ) * 100

Step 1 : Find formula weight of NaHCO₃

To find formula weight of NaHCO₃, we have to add atomic masses of the elements Na, H,C and O

Formula weight of NaHCO₃ = $Na+H+C+3 (O)$

Formula weight of NaHCO₃ = $22.99+1.01+12.01+3(16)$

Formula weight of NaHCO₃ is 84.01 g

Step 2 : Use percent by mass formula

Percent by mass of oxygen = (total mass of oxygen / formula weight) * 100

Percent by mass of oxygen = $\frac{3(16)}{84.01} * 100$

Percent by mass of oxygen = 57.14%

Answer : percentage by mass of oxygen in a formula unit of sodium hydrogen carbonate (NaHCO3) is 57.14%

Katen [24]3 years ago

7 0

((8×3)÷(11+1+6+16+(8×3)))×100

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Answer is: group 17 on the periodic table.

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a rock is examined to determine its age, and the ratio of uranium-235 to lead-207 is found to be 125,000:875,000. the half-life

slamgirl [31]

The old age of rock when examined is 21.4 million years if the ratio of uranium-235 to lead-207 is found to be 125,000:875,000. the half-life of uranium-235 is 700 million years.

<h3>Decaying Equation </h3>

P = [P + D] (1/2) ^(t/t(1/2))

where,

P represent the present parent amount

D is the present daughter amount

t(1/2) is the half life time period

t is the actual age

We know that,

t = (log[(P+D) /P] / log2) × t(1/2) ----------(1)

Given,

P = 97.6

D = 2.1

Ratio of P and D can be calculated as

P/D = 97.6/2.1

= 46.476

By substituting all the values in eq(1), we get

t = [(log 46.476 +1)/log2] × t(1/2)

Given,

The half life of U —Pb decay is 700 million years.

So,

t = [(log 46.476 +1)/log2] × 700

t = 21.4 million years.

Thus, we calculated that the the old age of rock when examined is 21.4 million years.

learn more about Half life period:

brainly.com/question/20309144

#SPJ4

DISCLAIMER:

The given question is misprint on portal.

Here is the correct form of question:

A rock is examined to determine its age, and the ratio of uranium-235 to lead-207 is found to be 125,000:875,000. the half-life of uranium-235 is 700 million years.

How old is the rock if it contains Uranium-235/ lead-207 ratio of 97.6 to 2.1?

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2 years ago

You have 2 moles of NaOH how many molecules of NaOH?

kaheart [24]

Answer:

12.044 X 10^23 molecules of NaOH

Explanation:

because NaOH is an ionic bond, we should be asking how many <em>formula units </em> are in 2 moles of NaOH, there are 0 molecules since NaOH is measured in formula units.

but for the sake of the problem I'll assume NaOH is measured in molecules

for every mol of something there are 6.022 X 10^23 of something of that something.

so there are 6.022 X 10^23 molecules for every mol of NaOH

that means we have 2 X 6.022 X 10^23 molecules in 2 moles of NaOH = 12.044 X 10^23 molecules of NaOH

4 0

3 years ago