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3 years ago

What is the empirical formula for a compound if a sample contains 3.72 g of P and 21.28 g of Cl?

1 answer:

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Given 3.72 g of P and 21.28g of Cl, converting these to moles: ( 3.72 g P)(mol P/30.97 g P) = 0.12 mol P (21.28 g Cl)(mol Cl/35.45 g Cl) = 0.60 mol Cl P:Cl = 0.12/0.60, therefore P: Cl =1/5 Therefore, PCl5 hope it helps

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Need asap! Step-by-step pls: Determine the empirical formula: 32.37% Na, 22.58% S, 45.05% O

Ludmilka [50]

1) divide each percentage by the relative atomic mass of the element

2) divide all results by the smallest number

3)multiply by a whole number to get the simplest whole number ratio (if necessary)

that is to say:

Na S O

32.37÷23 22.58÷32 45.05÷16

= 1.407 = 0.7056 = 2.816 (to 4 significant figures)

the smallest number here is 0.7056 so:

1.407÷0.7056 0.7056÷0.7056 2.816÷0.7056

=1.99 approx.2 = 1 3.99 approx. 4

here there is no need to carry out step 3 as ratio obtained is already a simplest whole number ratio

so empirical formula is: Na₂SO₄

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3 years ago

What is the kinetic energy of the emitted electrons when cesium is exposed to UV rays of frequency 1.3×1015Hz?

Sonja [21]

Answer:

We know that

ħf = ф + Ekmax

where

ħ = planks constant = 6.626x10^-34 J s

f = frequency of incident light = 1.3x10^15 /s (1 Hz =

1/s)

ф = work function of the cesium = 2.14 eV

Ekmax = max kinetic energy of the emmitted electron.

We distinguish that:

1 eV = 1.602x10^-19 J

So:

2.14 eV x (1.602x10^-19 J / 1 eV) = 3.428x10^-19 J

So,

Ekmax = (6.626x10^-34 J s) x (1.3x10^15 / s) - 3.428x10^-19 J

= 8.6138x10^-19 J - 3.428x10^-19 J = 5.1858x10^-19 J

Answer:

5.19x10^-19 J

Kinetic energy:

In physics, the kinetic energy of an object is the energy that it owns due to its motion. It is defined as the work required accelerating a body of a given mass from rest to its specified velocity. Having expanded this energy during its acceleration, the body upholds this kinetic energy lest its speed changes.

Answer details:

Subject: Chemistry

Level: College

Keywords:

• Energy

• Kinetic energy

• Kinetic energy of emitted electrons

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