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Serhud [2]
3 years ago
14

How many significant figures are in 0.00120

Chemistry
1 answer:
Svetllana [295]3 years ago
4 0
There are 3 significant figures
You might be interested in
A chemist has 3.55x1022 molecules of nitrogen monoxide. How
Alina [70]

Answer:

<h2>0.059 moles</h2>

Explanation:

To find the number of moles in a substance given it's number of entities we use the formula

n =  \frac{N}{L} \\

where n is the number of moles

N is the number of entities

L is the Avogadro's constant which is

6.02 × 10²³ entities

From the question we have

n =  \frac{3.55 \times  {10}^{22} }{6.02 \times  {10}^{23} }  \\  = 0.05897...

We have the final answer as

<h3>0.059 moles</h3>

Hope this helps you

6 0
3 years ago
What is the atomic mass?
labwork [276]

Answer:

Sonic has your answer The atomic mass is the mass of an atom. Although the SI unit of mass is kilogram, the atomic mass is often expressed in the non-SI unit dalton where 1 dalton is defined as ¹⁄₁₂ of the mass of a single carbon-12 atom, at res

8 0
3 years ago
Which of the following acids should be used to prepare a buffer with a pH of 4.5?A. HOC6H4OCOOH, Ka = 1.0 x 10^-3B. C6H4(COOH)2,
ioda

Answer:

C. CH3COOH, Ka = 1.8 E-5

Explanation:

analyzing the pKa of the given acids:

∴ pKa = - Log Ka

A. pKa = - Log (1.0 E-3 ) = 3

B. pKa = - Log (2.9 E-4) = 3.54

C. pKa = - Log (1.8 E-5) = 4.745

D. pKa = - Log (4.0 E-6) = 5.397

E. pKa = - Log (2.3 E-9) = 8.638

We choose the (C) acid since its pKa close to the expected pH.

⇒ For a buffer solution formed from an acid and its respective salt, we have the equation Henderson-Hausselbach (H-H):

  • pH = pKa + Log ([CH3COO-]/[CH3COOH])

∴ pH = 4.5

∴ pKa = 4.745

⇒ 4.5 = 4.745 + Log ([CH3COO-]/[CH3COOH])

⇒ - 0.245 = Log ([CH3COO-]/[CH3COOH])

⇒ 0.5692 = [CH3COO-]/[CH3COOH]

∴ Ka = 1.8 E-5 = ([H3O+].[CH3COO-])/[CH3COOH]

⇒ 1.8 E-5 = [H3O+](0.5692)

⇒ [H3O+] = 3.1623 E-5 M

⇒ pH = - Log ( 3.1623 E-5 ) = 4.5

6 0
3 years ago
Write the mole ratios of (2ca+o2➡2cao)
tresset_1 [31]
N(Ca)/2 = n(O)/1 = n(CaO)/2

The calcium and the Calcium Oxide are divided by 2 because of their coefficients
there is no number in front of the oxygen so it is over one.
Hope this helped!!
6 0
3 years ago
Read 2 more answers
What happens during every chemical change?
Aneli [31]
The chemical make-up changes.
6 0
3 years ago
Read 2 more answers
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