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Marat540 [252]
4 years ago
6

Which of these is an example of a physical change ?

Chemistry
1 answer:
Gre4nikov [31]4 years ago
8 0
It's 1. Melting a substance. The rest are chemical changes
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Which of these careers would a student studying biotechnology
matrenka [14]
I think it’s c I could be wrong
3 0
3 years ago
Draw the product of the reaction CH3CH2CH2CH2C?CCH3+2Br2??
svetlana [45]
I will assume that the sign ? between the C and the CCH3 is a triple bond, and I will represent it by three vertical lines |||


So the reaction is:


<span>CH3CH2CH2CH2C ||| CCH3+2Br2 ---->


This is a typical reaction known as halogenation of alkines.


This is an addition reaction, i.e. the alkyne undergoes an addition of the Br2 (and it also happens with Cl2) to the triple bond to form a tetra halide.


.
                                                                                                      Br   Br
</span>                                                                                                        |     |
<span><span>CH3CH2CH2CH2C ||| CCH3+2Br2 ---->  CH3 CH2 CH2 CH2 C - C</span> - CH3
                                                                                                        |     |
                                                                                                        Br   Br


</span>
3 0
3 years ago
Determine the [h3o+] of a 0.210 m solution of formic acid.
Nataly [62]
When the Pka for formic acid = 3.77
and Pka = -㏒ Ka 
   3.77 = -㏒ Ka
∴Ka = 1.7x10^-4 

when Ka = [H+][HCOO-}/[HCOOH]

when we have Ka = 1.7x10^-4 &[HCOOH] = 0.21 m
so by substitution: by using ICE table value
1.7x10^-4 = X*X / (0.21-X)
(1.7x10^-4)*(0.21-X) = X^2      by solving this equation for X

∴X = 0.0059
∴[H+] = 0.0059
∴PH= -㏒ [H+]
       = -㏒ 0.0059
       = 2.23 

3 0
3 years ago
1. Where do convection currents happen? crust inner core core mantle <br> pls help
Vikentia [17]

Answer:

Mantle

Explanation:

Convection currents in the Earth occur in the mantle. The core of the Earth is extremely hot, and material in the mantle close to the core is heated...

Hope that help <3

5 0
3 years ago
What is the pH of a solution of 0.800 M KH2PO4, potassium dihydrogen phosphate?
Nookie1986 [14]
KH₂PO₄ hydrolyzes as;
H₂PO₄⁻ + H₂O ↔ H₃PO₄ + OH⁻
Let x amount of H₂PO₄⁻ has reacted with water then,
Kb₁ = [H₃PO₄][OH⁻] / [H₂PO₄⁻]
[H₂PO₄⁻] = 0.8-x M
Kb₁ = x² / (0.8 - x)
Given Ka₁ = 7.5 x 10⁻³
so Kb₁ = 1 x 10⁻¹⁴ / (7.5 x 10⁻³) = 1.33 x 10⁻¹²
From this information:
1.33 x 10⁻¹² = x² / 0.8
x = [OH⁻] = 1.03 x 10⁻⁶ M
pOH = - log (1.03 x 10⁻⁶) = 5.99
pH = 14 - pOH = 14 - 5.99 = 8.01 



3 0
3 years ago
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