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4 years ago

Why are non-metals dull in appearance as solids?

1 answer:

6 0

Metalloids are metallic-looking brittle solids that are either semiconductors or exist in semiconducting forms, and have amphoteric or weakly acidic oxides. Typical nonmetals have a dull, coloured or colourless appearance; are brittle when solid; are poor conductors of heat and electricity; and have acidic oxides.

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What are deltaTb and deltaTf for an aqueous solution that is 1.5g nacl in 0.250kg h2o? Given Kb=0.51 C/m and kr=1.86 C/m

bulgar [2K]

Answer:

$T_f$ for given question is 2.79 and $T_b$ is 0.52

$\Delta T_b = I \times K_b \times m$ {i- vant hoff’s constant ; Kb- constant ; m molarity }

M = no. of moles of the solute present in one kg of solution

Let the weight of amount of solute be “w” and its molecular mass be “M”

Let the mass of the solvent in the given question be “x”

$\Delta T_b = I \times K_b \times (w/M)/ x$

$\Delta T_b = I \times K_b \times w/Mx$

$\Delta T_b = 1 \times 0.51 \times1.5/(0.250 \times 58.44) = 0.052$

$\Delta T_f = M \times K_f = 1.86 \times 1.5 = 2.79$

4 0

3 years ago

A piece of ice melts in one’s hand because heat moves from the hand into the ice. This is an example of heat transfer by .

SashulF [63]

Conduction which is a method of heat transfer where heat is transfer directly from one medium to another.

6 0

4 years ago

Read 2 more answers

A chemist determined by measurements that 0.015 moles of iron participated in a chemical reaction. Calculate the mass of iron th

exis [7]

Answer: 0.84 g

Explanation:

$\text{ Mass of iron}=\text{ Moles of iron}\times \text{ Molar mass of iron}$

Given: moles of iron = 0.015

Molar mass of iron = 56 g/mol

$\text{ Mass of iron}=0.015\times 56g/mol=0.84g$

Thus 0.84 g of iron participated in the chemical reaction.

7 0

3 years ago

How many moles of nitrogen we have at a temperature of 30 ?C, a pressure of 4.0 atm, and a volume of 4000.ML?

marishachu [46]

Answer:

0.643 mol.

Explanation:

We can use the general law of ideal gas: PV = nRT.

where, P is the pressure of the gas in atm (P = 4.0 atm).

V is the volume of the gas in L (V = 4000 mL = 4.0 L).

n is the no. of moles of the gas in mol (n = ??? mol).

R is the general gas constant (R = 0.0821 L.atm/mol.K),

T is the temperature of the gas in K (T = 30ºC + 273 = 303 K).

∴ n = PV/RT = (4.0 atm)(4.0 L)/(0.0821 L.atm/mol.K)(303 K) = 0.643 mol.

3 0

4 years ago

A 35.0 mL sample of 1.00 M KBr and a 60.0 mL sample of 0.600 M KBr are mixed. The solution is then heated to evaporate water unt

Katarina [22]

Answer: The molarity of KBr in the final solution is 1.42M

Explanation:

We can calculate the molarity of the KBr in the final solution by dividing the total number of moles of KBr in the solution by the final volume of the solution.

We will first calculate the number of moles of KBr in the individual sample before mixing together

In the first sample:

Volume (V) = 35.0 mL

Concentration (C) = 1.00M

Number of moles (n) = C × V

n = (35.0mL × 1.00M)

n= 35.0mmol

For the second sample

V = 60.0 mL

C = 0.600 M

n = (60.0 mL × 0.600 M)

n = 36.0mmol

Therefore, we have (35.0 + 36.0)mmol in the final solution

Number of moles of KBr in final solution (n) = 71.0mmol

Now, to get the molarity of the final solution , we will divide the total number of moles of KBr in the solution by the final volume of the solution after evaporation.

Therefore,

Final volume of solution (V) = 50mL

Number of moles of KBr in final solution (n) = 71.0mmol

From

C = n / V

C= 71.0mmol/50mL

C = 1.42M

Therefore, the molarity of KBr in the final solution is 1.42M

5 0

3 years ago