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bija089 [108]
3 years ago
9

______________ have properties of both metals and non metals.

Chemistry
1 answer:
stepan [7]3 years ago
4 0

Answer:

gold

Explanation:

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Each isotope has a unique half-life. The half-life of an isotope is the time taken for half of the starting quantity to decay (w
Tems11 [23]

Answer:

b. 17,190

Explanation:

Using the formula for C-14 dating,

t=\dfrac{ln(\dfrac{N}{N_0})t_\frac{1}{2}  }{-0.693}

where Present Value N =1/8 of Parent Sample

Initial Value, N_0=1

Half Life, t_\frac{1}{2}=5730 years

t=\dfrac{ln(\dfrac{1/8}{1})5730}{-0.693}

=17,190

Therefore the fossil is about 17190 years old.

7 0
3 years ago
Why is only one diastereomer formed in this reaction? Relate your answer to the mechanism you drew. b) If you used cis-stilbene
crimeas [40]

Answer:

1. Diastereomers have different physical properties (unlike most aspects of enantiomers) and often different chemical reactivity. ... Many conformational isomers are diastereomers as well. Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction.

2. The result is a trans dibromide, as shown in the equation below

Explanation:

Diastereomers (sometimes called diastereoisomers) are a type of a stereoisomer.[1] Diasteoreomers are defined as non-mirror image non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.[2] When two diastereoisomers differ from each other at only one stereocenter they are epimers. Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two.

2. the addition of bromine to the trans and

cis isomers of 1,2-diphenylethene, more commonly known as trans- and cis-stilbene.

H

H

H H

trans-stilbene cis-stilbene

m.p. 122-124°C b.p. 82-84°C

density 0.970 g/mL density 1.011 g/mL

M.W. 180.25 g/mol M.W. 180.25 g/mol

In both cases, the nucleophilic double bond undergoes an electrophilic addition reaction

by the bromine reagent which proceeds via a cyclic bromonium ion. The addition of

bromine begins at one side of the double bond (either side is equally likely, but only one

option is drawn) and is followed by attack of bromide ion on the bromonium ion (again,

attack could occur at either carbon since the ion is symmetric, but only one option is

drawn). The result is a trans dibromide, as shown in the equation below:

Since the cis and trans isomers of stilbene have different geometries, it follows

that upon reaction with bromine they give rise to stereoisomeric bromonium ions and,

eventually, products that differ only by their stereochemistry.

4 0
3 years ago
One of relatively few reactions that takes place directly between two solids at room temperature is <img src="https://tex.z-dn.n
kolbaska11 [484]

Answer:

a) Ba(OH)₂.8H₂O(s) + <em>2 </em>NH₄SCN(s) → Ba(SCN)₂(s) +<em>10</em> H₂O(l) + <em>2</em> NH₃(g)

b) 3.14g must be added

Explanation:

a) For the reaction:

Ba(OH)₂.8H₂O(s) + NH₄SCN(s) → Ba(SCN)₂(s) + H₂O(l) + NH₃(g)

As you see, there are 8 moles of water in reactants and 2 moles of oxygen in octahydrate, thus, water moles must be 10:

Ba(OH)₂.8H₂O(s) + NH₄SCN(s) → Ba(SCN)₂(s) +<em>10</em> H₂O(l) + NH₃(g)

To balance hydrogens, the other coefficients are:

Ba(OH)₂.8H₂O(s) + <em>2 </em>NH₄SCN(s) → Ba(SCN)₂(s) +<em>10</em> H₂O(l) + <em>2</em> NH₃(g)

b) As you see in the balanced reaction, 1 mole of barium hydroxide octahydrate reacts with 2 moles of NH₄SCN. 6.5g of Ba(OH)₂.8H₂O are:

6.5 g × (1mol / 315.48g) =<em> 0.0206moles of  Ba(OH)₂.8H₂O</em>. Thus, moles of NH₄SCN that must be used for a complete reaction are:

0.0206moles of  Ba(OH)₂.8H₂O × ( 2 mol NH₄SCN / 1 mol Ba(OH)₂.8H₂O) = <em>0.0412moles of NH₄SCN</em>. In grams:

0.0412moles of NH₄SCN × ( 76.12g / 1mol) = <em>3.14g must be added</em>

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3 years ago
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The compound MgF is an example of a(n)
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MgF is an ionic compound because it's bond is between a metal and a non-metal
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Why is reading important in science?
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<span>Dispelling the perception that Indian scientists are averse to advertising their work, recipient of this year's Shanti Swarup Bhatnagar prize, Dr.Eknath Ghate and Dr.Amol Dighe, said that in science, it is important to publish and publicise one's work globally. </span>
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