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irinina [24]
3 years ago
12

Petunia needs 66.48 grams of potassium hydroxide (KOH) to run a reaction in class. How many moles of potassium hydroxide does sh

e need? Please round your answer to two digits after the decimal point, and remember to include correct, complete units (including substance formula).
Chemistry
1 answer:
Kaylis [27]3 years ago
4 0

Answer:

She needs 1.19 moles of potassium hydroxide.

Explanation:

Being the molar mass of the elements:

  • K= 39 g/mole
  • O= 16 g/mole
  • H= 1 g/mole

then the molar mass of potassium hydroxide is:

KOH= 39 g/mole + 16 g/mole + 1 g/mole= 56 g/mole

Being the mass of one mole of a substance, which can be an element or a compound, you can apply the following rule of three: if 56 g of KOH are present in 1 mole, 66.48 g of KOH in how many moles of the compound are they?

moles of KOH=\frac{66.48 grams*1 mole}{56 grams}

moles of KOH= 1.19

<u><em> She needs 1.19 moles of potassium hydroxide.</em></u>

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A person’s blood alcohol (C2H5OH) level can be determined by titrating a sample of blood plasma
Elanso [62]

Answer:

0.17%

Explanation:

With the equation:

2Cr2O7 2- + C2H5OH + H2O --> 4Cr3+ + 2CO2 + 11H2O

We can assume that every mole of ethanol needs 2 moles of Dichromate to react.

So if in 1L we have 0.05961 moles of dichromate we can discover how many moles we have in 35.46mL

1000 mL - 0.05962 moles

35.46 mL - x

x = \frac{0.05962 * 35.46}{1000}

x = 2,11* 10^-3 moles

As we said earlier, 1 mole of ethanol needs 2 mole of dichromate, so in the solution we have 1,055*10^-3 moles of ethanol. We can discover the mass of ethanol present in the solution.

1 mole - 46g

1.055*10^-3 - y

y = 46 * 1.055*10^-3

y = 0.048 g

To discover the percent of alchol we can use a simple relation

28 g - 100%

0.048 - z

z = \frac{0.048 * 100}{28}

z = 0.17%

6 0
3 years ago
What is the ionic compound of Na^+ and CO3^2-
maksim [4K]

To find the chemical formula of an ionic compound, the first step is to find the charge of the 2 ions. As given already, the charge of sodium ion is 1+, and carbonate ion has a charge of 2-. We can picture it like that: Sodium ion loses 1 electron and carbonate ion gains 2.

The next step is to find how the 2 ions can lose and gain electrons equally. In this case, since each Na ion only loses 1 electron, it cannot satisfy the need of one carbonate ion, since they need 2, not 1. Therefore, 2 Na ions can cover the need of one carbonate ion. So, the ratio of Na to CO3 ion should be 2:1.

Now just combine the 2 ions, positive one at the front, which makes it NaCO3, make sure you do not add the charge and notice that CO3 is a molecule itself so do not remove the 3. Now because the ratio is 2:1, so the final formula is Na2CO3, no need to add 1 if the ratio is 1.

Your answer should be Na2CO3.

8 0
3 years ago
At pH= 8, which species is most likely to predominate in solution? pKa (-NH3+) = 9.9, pKa (-COOH) = 2.3
PtichkaEL [24]

Answer:

The NH3 + with a PKa = 9.9

Explanation:

The Pka is a mathematical expression to express the dissociation grade of a substance in a solution, that means with a substance with a pKa small is a strong acid, and in this case since the solution pH is 8, that mean that the substance with high pKa ( lower acid strength)  will predominate in a pH of 8.

7 0
3 years ago
The Positively charged center of an atom is called
Rashid [163]

Answer: The Nucleus: The Center of an Atom. The nucleus, that dense central core of the atom, contains both protons and neutrons. Electrons are outside the nucleus in energy levels. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.

5 0
3 years ago
why is it necessary to adjust the height of the graduated cylinder when measuring the volume of co2 (g) produced? group of answe
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3. The height of the graduated cylinder when measuring the volume of co2 (g) produced is adjusted to equalize the pressure in the graduated cylinder with the atmospheric pressure.

We discovered that when the water level within the graduated cylinder is higher than the water level outside, the gases inside the graduated cylinder have a lower pressure than the atmospheric pressure. It would then be possible to equalize pressure by changing the graduated cylinder's water level to match the water level outside.

Therefore last option or 3rd option is the correct choice.

For more questions like Cylinder click the link below:

brainly.com/question/14085192

#SPJ4

5 0
1 year ago
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