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9966 [12]
3 years ago
9

Element X is found in two forms: 90.0% is an isotope that has a mass of 20.0, and 10.0% is an isotope that has a mass of 22.0. W

hat is the atomic mass of element X?
A. 20.0
B. 20.2
C. 20.8
D. 21.2
E. 21.8
Can anyone explain this one for me?
Chemistry
1 answer:
VMariaS [17]3 years ago
7 0
M_{X} = \frac{(20.0\cdot 90\%)+(22.0\cdot10\%)}{100\%} = \frac{2020}{100} = 20.2[u]

answer: B
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_AI + _HCI —> _H2 + _AlCl3
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Hey there!

Al + HCl → H₂ + AlCl₃

Balance Cl.

1 on the left, 3 on the right. Add a coefficient of 3 in front of HCl.

Al + 3HCl → H₂ + AlCl₃

Balance H.

3 on the left, 2 on the right. We have to start by multiplying everything else by 2.

2Al + 3HCl → 2H₂ + 2AlCl₃

Now we have 2 on the right and 4 on the left. Change the coefficient in front of HCl from 3 to 4.

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2Al + 6HCl → 3H₂ + 2AlCl₃  

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2 on the left, 2 on the right. Already balanced.

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Which of the following is a way in which elements and compounds are similar?
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Answer:

Compound Element

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A sample was prepared by mixing 18. ml of 3.00 x 10^-3 m crystal violet (cv) with 2.00 ml of 0.250 m naoh. calculate the resulti
Aleks [24]

Answer : The resulting concentrations of CV and NaOH are 0.0027 M and 0.025 M respectively.

Explanation :

Step 1 : Find moles of crystal violet and NaOH.

The molarity formula is

Molarity = \frac{mol}{L}

Molarity of crystal violet = 3.00 \times 10^{-3} = \frac{mol (CrystalViolet)}{L}

The volume of crystal violet solution is 18 mL which is 0.018 L.

Moles of crystal violet = 3.00 \times 10^{-3} \times 0.018 = 5.4 \times 10^{-5}

Moles of crystal violet = 5.4 x 10⁻⁵

Moles of NaOH = Molarity \times L = 0.250 \times 0.00200 = 5.00 \times 10^{-4}

Moles of NaOH = 5.00 x 10⁻⁴

Step 2 : Find total volume of the solution

The total volume of the solution after mixing NaOH and crystal violet is

0.018 L + 0.00200 = 0.020 L

Step 3 : Use molarity formula to find final concentrations

Molarity of crystal violet = \frac{mol(CrystalViolet)}{Total Volume(L) } = \frac{5.4 \times 10^{-5}}{0.020} = 2.7 \times 10^{-3}

Final concentration of CV = 0.0027 M

Molarity of NaOH= \frac{mol(NaOH)}{Total Volume(L) } = \frac{5.00 \times 10^{-4}}{0.020} = 0.025 \times 10^{-3}

NaOH is a strong base and dissociates completely as follows.

NaOH (aq) \rightarrow Na^{+} (aq) + OH^{-} (aq)

The mole ratio of NaOH and OH⁻ is 1:1 . Therefore the concentration of OH⁻ is same as that of NaOH.

Concentration of OH⁻ = 0.025 M

8 0
3 years ago
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