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antiseptic1488 [7]
3 years ago
8

A 0.7834 g sample of a primary standard KHP was titrated with 38.45 mL of NaOH solution to a phenolphthalein end-point. What is

the molarity of the NaOH solution?
Chemistry
1 answer:
Zinaida [17]3 years ago
6 0

Answer:

0.0998 M

Explanation:

KHP is a weak <em>monoprotic</em> acid. This means that t<u>he moles of acid are equal to the moles of OH⁻ that were added in the titration</u>.

KHP Molecular weight = 204.22 g/mol

  • moles KHP = 0.7834 g ÷ 204.22 g/mol = 3.836x10⁻³ mol KHP

So  3.836x10⁻³ moles of OH⁻ were added in the titration. With moles and volume we can <u>calculate the molarity of the NaOH solution</u>:

38.45 mL ⇒ 38.45/1000 = 0.03845 L

  • 3.836x10⁻³ mol OH⁻ / 0.03845 L = 0.0998 M
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Which formula is an empirical formula?
poizon [28]
<h2>Hello!</h2>

The answer is:

The empirical formula is the option B. NH_{3}

<h2>Why?</h2>

The empirical formula of a compound is the simplest formula that can be written. On the opposite, the molecular formula involves a variant of the same compound, but it can be also simplified to an empirical formula.

MolecularFormula=n(EmpiricalFormula)

We are looking for a formula that cannot be simplified by dividing the number of molecules/atoms that conforms the compound.

Let's discard option by option in order to find which formula is an empirical formula (cannot be simplified)

A. N_{2}O_{4}

It's not an empirical formula, it's a molecular formula since it can be obtained by multiplying the empirical formula of the same compound.

N_{2}O_{4}=2(NO_{2})

B. NH_{3}

It's an empirical formula since it cannot be obtained by the multiplication of a whole number and the simplest formula. It's the simplest formula that we can find of the compound.

C. C_{3}H_{6}

It's not an empirical formula, it's a molecular formula since it can be obtained by multiplying the empirical formula of the same compound.

C_{3}H_{6}=3(CH_{2})

D. P_{4}O_{10}

It's not an empirical formula, it's a molecular formula since it can be obtained by multiplying the empirical formula of the same compound.

P_{4}O_{10}=2(P_{2}O_{5})

Hence, the empirical formula is the option B. NH_{3}

Have a nice day!

6 0
3 years ago
Read 2 more answers
Please please help:(
borishaifa [10]
Magnesium and silver
4 0
3 years ago
Why is important to only test one variable at a time?
Natalija [7]

Answer:

B

Explanation:

It is important to only test one variable at a time because you need to be able to disprove or prove a problem with just one independent variable. When you have several variables in the experiment, it would be impossible to know which variable honestly caused the end result.

4 0
2 years ago
A piece of material with a mass of 755 g is heated to 84.5 c and added to 50 g of water at 5
lana [24]
Alright sorry you're getting the answer hours later, but i can help with this.
so you're looking for specific heat, the equation for it is <span>macaΔTa = - mbcbΔTb with object a and object b. that's mass of a times specific heat of a times final minus initial temperature of a equals -(mass of b times specific heat of b times final minus initial temperature of b)
</span>so putting in your values is, 755g * ca * (75 celsius - 84.5 celsius) = -(50g * cb * (75 celsius - 5 celsius))
well we know the specific heat of water is always 4180J/kg celsius, so put that in for cb
with a bit of simplification to the equation by doing everything on each side first you have, -7172.5 * ca = -14630000
divide both sides by -7172.5 so you can single out ca and you get, ca= 2039.74
add units for specific heat which are J/kg celsius and the specific heat of the material is 2039.74 J/kg celsius

6 0
4 years ago
A 20 ml sample of .875 m hcl solution was diluted t o150 ml. calculate the molarity of the resulting solution
Veronika [31]
0.11666667 because M1V1=M2V2
4 0
3 years ago
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