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4 years ago

Why is silicon used to make PV cells

1 answer:

3 0

Silicon is used in producing Pv celss because cells made from the crystallized polycrystalline silicon have efficiencies in the range of 14-18% and a moderate price.

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10 To become positively charged, an atom must: A Galn a proton B Lose a proton C С. Galn an electron D Lose an electron }

Studentka2010 [4]

Answer:

D: lose an electron

Explanation:

when an atom loses an electron it's positively charged and when it gain an electron it is negatively charged

6 0

3 years ago

Which factor most likely facilitates mass movement after heavy rains in a dry region?

melomori [17]

Answer: Option (b) is the correct answer.

Explanation:

The process in which sediment moves downhill is known as mass movement.

Different types of mass movement are landslides, mud slides, slump, creep etc.

Mud flow contains mass of saturated rock particles of all sizes. Mud flow arises due to sudden flood of water or due to heavy rain in a dry region (semi-arid region). Soil and rocks from a large slope area flow along with the flood water and gets washed to a gulch or canyon.

As a result, debris and water moves down canyon and lay out on the gentle slopes below.

Thus, we can conclude that mud flow is most likely facilitates mass movement after heavy rains in a dry region.

4 0

3 years ago

Read 2 more answers

Which of the following is not equal to 42.7 millimeters?

Stella [2.4K]

The answer is: C. 0.00427 m.

A) 1 km = 1000000 mm.

d = 0.0000427 km · 1000000 mm/km.

d = 47.7 mm.

B) 1 hm = 100000 mm.

d = 0.000427 hm · 100000 mm/hm.

d = 42.7 mm.

C) 1 m = 1000 mm.

d = 0.00427 m · 1000 mm/m.

d = 4.27 mm.

D) 1 cm = 10 mm.

d = 4.27 cm · 10 mm/cm.

d = 42.7 mm.

Millimeter (abbreviated: mm, a thousandth part of metar) is an unit of distance in the metric system.

8 0

4 years ago

An environmental scientist developed a new analytical method for the determination of cadmium (cd^2+) in mussels. To validate th

Anettt [7]

Answer:

The method is accurate in the calculation of the $Cu^+2$

Explanation:

As a first step we have to calculate the average concentration of $Cu^+2$ find it by the method.

$\frac{0.782+0.762+0.825+0.838+0.761 }{5} =0.79 ppm$

Then we have to find the standard deviation:

$s=\sqrt{\frac{1}{N-1}\sum_{i=1}^N(x_i-\bar{x})^2}=0.0359$

For the confidence interval we have to use the formula:

μ=Average± $\frac{t*s}{\sqrt{n} }$

Where:

t=t student constant with 95 % of confidence and 5 data=2.78

μ= $0.79$ ± $\frac{2.78*0.0359}{\sqrt{5} }$

upper limit: 0.84

lower limit: 0.75

If we compare the limits of the value obtanied by the method (Figure 1 Red line) with the reference material (Figure 1 blue line) we can see that the values obtained by the method are within the values suggested by the reference material. So, it's method is accurate.

7 0

3 years ago

A student who is performing this experiment pours an 8.50 mL sample of the saturated borax solution into a 10 mL graduated cylin

gtnhenbr [62]

Answer:

ksp = 0,176

Explanation:

The borax (Na₂borate) in water is in equilibrium, thus:

Na₂borate(s) ⇄ borate²⁻(aq) + 2Na⁺(aq)

When you add just borax, the moles of Na²⁺ are twice the moles of borate²⁻, that means 2borate²⁻=Na⁺ (1)

The ksp is defined as:

ksp = [borate²⁻] [Na⁺]²

Then, borate²⁻(B₄O₇²⁻) reacts with HCl thus:

B₄O₇²⁻ + 2HCl + 5H₂O → 4H₃BO₃ + 2Cl⁻

The moles of HCl that reacts with B₄O₇²⁻ are:

0,500M×0,01200L = 6,00x10⁻³ mol of HCl

As two moles of HCl react with 1 mol of B₄O₇²⁻, the moles of B₄O₇²⁻ are:

6,00x10⁻³ mol of HCl× $\frac{1molB_{4}O_{7}^{2-}}{2molHCl}$ = 3,00x10⁻³ mol of B₄O₇²⁻

For (1), moles of Na⁺ are 3,00x10⁻³ mol ×2 = 6,00x10⁻³ mol of Na⁺

The [borate²⁻] is 3,00x10⁻³ mol of B₄O₇²⁻/0,00850L = 0,353M

And [Na⁺] is 6,00x10⁻³ mol of Na⁺ / 0,00850L = 0,706M

Replacing in the expression of ksp:

ksp = [0,353] [0,706]²

ksp = 0,176

I hope it helps!

8 0

3 years ago