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2 years ago

Round off each of the following numbers to two significant figures:

Chemistry

2 answers:

Kay [80]2 years ago

7 0

A) 5.2 x 10^2
B) 86.
C) 6.4 x 10^3
D) 5.0
E) 22.
F) 0.89

strojnjashka [21]2 years ago

7 0

Answer:

(a) 5.1 × 10²

(b) 86

(d) 5.0

(e) 22

(f) 0.89

Explanation:

To round off a number, we consider the number that is to its right. If that number is 5 or higher, we increase the number of interest. If the number to the right is 4 or lower, the number of interest remains the same. When taking less significant figures, we might need to use scientific notation for large or small numbers.

Round off each of the following numbers to two significant figures:

(a) 517 → 5.1 × 10²

(b) 86.3 → 86

(c) 6.382 × 10³ → 6.4 × 10³

(d) 5.0008 → 5.0

(e) 22.497 → 22

(f) 0.885 → 0.89

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2 years ago

The nuclear equation is incomplete. Superscript 239 Subscript 94 Baseline P u + Superscript 1 Subscript 0 Baseline n yields Supe

Likurg_2 [28]

Answer:

The correct option is the first option

Explanation:

The equation described in the question is shown below

²³⁹₉₄Pu +¹₀n ⇒ ¹⁰⁰₄₀Zr + blank + 2¹₀n

This equation is a nuclear fission because it involves the splitting of a heavy nucleus, Plutonium (Pu), into smaller nuclei, Zirconium (Zr) and an unknown nuclei.

The law of conservation of matter states that matter can neither be created nor destroyed hence in other to get the missing atom, we must know the total number of subscripts (mass number) and superscripts (atomic number) on both sides.

The total mass number on the reactant side is 239 + 1 = 240

The total atomic number on the reactant side is 94 + 0 = 94

While, The total mass number on the product side is 100 + 2(1) = 102

The total atomic number on the product side is 40 + 2(0) = 40

To determine the missing atom, you subtract the the total atomic number of the product from that on the reactant side; 94 - 40 = 54

The atom with the atomic number 54 is Xenon,

To determine the mass number of the xenon isotope involved, you subtract the the total mass number of the product from that on the reactant side; 240 - 102 = 138.

Hence, the particle that completes the equation is ¹³⁸₅₄Xe, the first option

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2 years ago

A ground state hydrogen atom absorbs a photon of light having a wavelength of 93.7 nm.93.7 nm. What is the final state of the hy

sammy [17]

Answer:

Explanation:

Given that the formula is;

1/λ= R(1/nf^2 - 1/ni^2)

λ = 93.7 nm or 93.7 * 10^-9 m

R= 1.097 * 10^7 m-1

nf = ?

ni = 1

From;

ΔE = hc/λ

ΔE = 6.63 * 10^-34 * 3* 10^8/93.7 * 10^-9

ΔE = 21 * 10^-19 J

ΔE = -2.18 * 10^-18 J (1/nf^2 - 1/ni^2)

21 * 10^-19 J = -2.18 * 10^-18 J (1/nf^2 - 1/ni^2)

21 * 10^-19/-2.18 * 10^-18 = (1/nf^2 - 1/1^2)

-0.963 = (1/nf^2 - 1)

-0.963 + 1 = 1/nf^2

0.037 = 1/nf^2

nf^2 = (0.037)^-1

nf^2 = 27

nf = 5

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2 years ago

Which pair of statements below is correct? Multiple Choice An octet is formed via ionic bonding when one or more valence electro

tresset_1 [31]

Answer:

An octet is formed via ionic bonding when one or more valence electrons are transferred from one atom to another.

An octet is formed via covalent bonding when valence electrons are shared between atoms.

An octet is always formed via ionic bonding

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2 years ago

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. Calculate the mass of O2 produced if 3.450 g potassium chlorate is completely decomposed by heating in presence of a catalyst

Vesnalui [34]

2 KClO3(s) → 3 O2(g) + 2 KCl(s)

Note: MnO2 (Manganese Dioxide) is not part of the reaction. A catalyst lowers the activation energy and increases both forward and reverse reactions at equal rates.

molar mass of KClO3 = 122.5
Moles of KClO3 = 3.45 / 122.55 = 0.028

Moles of O2 produce = $\frac{3}{2} \times 0.028$

= 0.042 moles

molar mass of O2 = 32

so, mass of O2 = 32 x 0.042 = 1.35 g

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2 years ago