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RSB [31]
3 years ago
14

Borax (na2b4o7·10h2o; fw = 381.372 g/mol; density = 1.73 g/ml), a primary standard, was used to standardize a solution of hno3.

titration of 0.2619 g of borax required 21.61 ml. what is the molarity of the hno3
Chemistry
1 answer:
SashulF [63]3 years ago
3 0
<span>0.06355391 mol The balanced equation for the reaction is Na2B4O7*10H2O + 2 HNO3 = 2 NaNO3 + 4 H3BO3 + 5 H2O So for each mole of Borax to neutralize, it takes 2 moles of HNO3. Calculate number of moles of Borax 0.2619 g / 381.372 g/mol = 0.0006867 mol Moles of HNO3 used = 0.0006867 mol * 2 = 0.0013734 mol Molarity is defined as moles per liter so divide the number of moles used by the volume in liters. So 0.0013734 / 0.02161 = 0.06355391 mol</span>
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Electron A falls from energy level X to energy level Y and releases blue light. Electron B falls from energy level Y to energy l
MrMuchimi

Answer: Transition from X to Y will have greater energy difference.

Explanation: For studying the energy difference, we require Planck's equation.

                                E=\frac{hc}{\lambda}

where, h = Planck's Constant

c = Speed of light

E = Energy

\lambda = Wavelength of particle

From the equation, it is visible that the energy and wavelength follow inverse relation which means that with low wavelength value, energy will be the highest and vice-versa.

As electron A falls from X-energy level to Y-energy level, it releases blue light which has low wavelength value (around 470 nm) which means that it has high energy.

Similarly, Electron B releases red light when it falls from Y-energy level to Z-energy level, which has high wavelength value (around 700 nm), giving it a low energy value.

Energy Difference between X-energy level and Y-energy level will be more.


5 0
3 years ago
Predict: Will a 1500 kg car moving at the same speed as the tennis ball have
sergeinik [125]
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4 0
2 years ago
An investor has an account with stock from two different companies. Last year, his stock in Company A was worth $7200 and his st
djyliett [7]

Answer:

22.7%

Explanation:

Given that last year stock for company A was $7200

The stock for company B last year was worth $3510

Stock in company A decreased by 24%

This means the new value of stock for company A became;

(100-24)/100 *$7200

76/100*$7200

0.76*7200 =$5472

Stock in company B decreased by 20%

This means the new value of stock for company B became;

(100-20)/100 *$3510

80/100*$3510

0.8*$3510

$2808

Original investors stock value was = $7200+$3510 =$10710

New investors stock value is = $5472+$2808=$8280

Decrease in value of stock = $10710-$8280 =$2430

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7 0
2 years ago
Estimate the Calorie content of 65 g of candy from the following measurements. A 15-g sample of the candy is placed in a small a
GrogVix [38]

Answer:

The calorie content of  65g of candy is 326.78 cal

Explanation:

Step 1: Data given

Mass of the candy = 15.00 grams

Mass of the container = 0.325 kg

Mass of water = 1.75kg

0.624 kg at an initial temperature of 15.0°C.

The specific heat of aluminium = 0.22 Cal/kg°C

The specific heat of water = 1 cal/kg°C

Step 2: Calculate calorie content for a 15 gram sample

ΔQ = Σm*c*ΔT

 ⇒ m = mass in grams

⇒ with c= the specific heat in Cal/kg°C

⇒ with ΔT = T2 -T1 = the change in temperatures in °C

ΔQ = m(bomb) * C(aluminium) * ΔT + m(cup) * C(aluminium) * ΔT + m(H2O) * c(H20) * ΔT

ΔQ = (m(bomb) + m(cup)) * c(aluminium)  + m(H2O)*c(H20) ) * ΔT

⇒ with mass of the bomb calorimeter = 0.325 kg

⇒ with mass of the cup = 0.624 kg

⇒ with c(aluminium) = the specific heat of aluminium = 0.22 Cal/kg°C

⇒ with mass of water = 1.75 kg

⇒ with c(water) = the heat capacity of water = 1 Cal/kg°C

⇒ with ΔT = the change in temperature = T2 - T1 = 53.5 - 15.0 = 38.5 °C

ΔQ = 0.325*0.22*38.5 + 0.624*0.22*38.5 + 1.75*1*38.5

ΔQ = ((0.325 + 0.624)*0.22 + 1.75*1)*38.5

ΔQ = 75.41 cal

Step 3: Calculate the calorie content for a 65 gram sample

For a 65g sample the calorie content will be more or less 4x higher than a 15 gram sample:

ΔQ = 75.41  * (65/15) = 326.78 cal

8 0
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