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ruslelena [56]
2 years ago
13

In a lab, calcium chloride is dissolved in water in a test tube. As it dissolves the test tube gets warmer. Which of these is a

good explanation for this?
A.) This is an endothermic reaction
B.) As the solute dissolves it gives off heat to the surrounds.
C.) As the solute dissolves it takes heat from the surrounds
D.A contaminant must have been present in the water as mixing never creates heat.
Chemistry
2 answers:
Luden [163]2 years ago
5 0
The answer is B.. solute dissolves guves off what to the surrounds
kozerog [31]2 years ago
4 0

Answer:

B

Explanation:

The mixture gave off heat

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Answer:

Explanation:

Inertia is the reluctancy of a moving body to come to rest or change it direction or a body at rest to start moving

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4 years ago
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Two chemicals A and B are combined to form a chemical C. The rate, or velocity, of the reaction is proportional to the product o
stiv31 [10]

Answer:

Follows are the solution:

Explanation:

A + B = C

Its response decreases over time as well as consumption of a reactants.  

r = -kAB

during response A convert into 2x while B convert into x to form 3x of C

let's  y = C

y = 3x

Still not converted sum of reaction  

for A: 100 - 2x

for B: 50 - x

Shift of x over time  

\frac{dx}{dt} = \frac{-k(100 - 2x)}{(50 - x)}

Integration of x as regards t  

\frac{1}{[(100 - 2x)(50 - x)]} dx = -k dt\\\\\frac{1}{2[(50 - x)(50 - x)]} dx = -k dt\\\\\ integral\  \frac{1}{2[(50 - x)^2]} dx =\ integral [-k ] \ dt\\\\\frac{-1}{[100-2x]} = -kt + D \\\\

D is the constant of integration

initial conditions: t = 0, x = 0

\frac{-1}{[100-2x]} = -kt + D   \\\\\frac{ -1}{[100]} = 0 + D\\\\D= \frac{-1}{100}\\\\

hence we get:

\frac{-1}{[100-2x]}= -kt -\frac{1}{100}\\\\or \\\\ \frac{1}{(100-2x)} = kt + \frac{1}{100}

after t = 7 minutes , C = 10 \ g = 3x

3x = 10\\\\x = \frac{10}{3}

Insert the above value x into \frac{1}{(100-2x)} equation = kt + \frac{1}{100} to get k.  

\to  \frac{1}{(100-2\times \frac{10}{3})}  = k \times (7) + \frac{1}{100} \\\\ \to  \frac{1}{(100- 2 \times 3.33)} =   \frac{700k + 1}{100} \\\\ \to  \frac{1}{(100-6.66)} = \frac{700k + 1}{100}\\\\ \to \frac{1}{93.34} = \frac{700k + 1}{100} \\\\

\to 100 =  93.34(700k + 1) \\\\ \to 100 =  65,338k + 700 \\\\ \to   65,338k =  -600 \\\\ \to  k =  \frac{-600}{ 65,338} \\\\ \to k= - 0.0091

therefore plugging in the equation the above value of k  

\to \frac{1}{(100-2x)} = kt +\frac{1}{100} \\\\\to \frac{1}{(100-2x)} = -0.0091t + \frac{1}{100}\\\\\to \frac{1}{(100-2x)} =  \frac{1 -0.91t}{100}\\\\\to \frac{1}{2(50-x)} =  \frac{1 -0.91t}{100}\\\\\to \frac{1}{(50-x)} =  \frac{1 -0.91t}{50}\\\\\to 50= (1-0.91t)(50-x)\\\\\to 50 = 50-45.5t-x-0.91tx\\\\\to x+0.91xt= -45.5t\\\\\to x(1+0.91t)= -45.5t\\\\\to x=\frac{-45.5t}{1+0.91t}

Let y = C

, calculate C:

y = 3x

y =3 \times \frac{-45.5t}{1+0.91t}

amount of C formed in 28 mins

x = \frac{-45.5t}{1+0.91t} , plug t = 28

\to x = \frac{-1274}{1+25.48} \\\\\to x = \frac{-1274}{26.48} \\\\\to x= -48.26

therefore amount of C formed in 28 minutes is = 3x = 144.78 grams

C: y =3 \times \frac{-45.5t}{1+0.91t}

y= 136.5 =137

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Which of the following has the highest electronegativity?<br> A. Na <br> B. Li<br> C. C<br> D. Si
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Answer:

C. C, because it’s the highest of all four and C is 2,5 which is medium but the highest one.

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It is given that the charge on potassium is +1 i.e. Potassium is a cation, K⁺

The charge on selenium is given as -2, i.e. selenium is an anion, Se²⁻

The two ions are shown to combine to form a molecule: KXSeY where X and Y correspond to the proportions in which the two atoms combine.

Since the molecule is neutral, the positive and negative charges need to be balanced. This is possible only if 2 units of K⁺ combines with 1 unit of Se²⁻.

Therefore, the formula would be K₂Se

X = 2 and Y = 1

3 0
4 years ago
What masses of KCl and H2O are needed to make 250 g of 5.00 % solution?
oksano4ka [1.4K]

Answer:

w/w means weight/weight

Therefore, in a 250 g of solution, 5% needs to be KCl,  

i.e. 5% x 250 = 12.5 g of KCl is needed.

7 0
3 years ago
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