Which of these is an example of physical change?

1 answer:

6 0

A. Boiling water is an example of physical change, whereas digesting food, breaking glass, and shoveling snow are not.

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ASAP: in group 13, the only metalloid, boron, is at the very top of the group. Explain why the rest of the group has metallic be

Marrrta [24]

Electronegativity of boron is the highest in the group and it will form covalent bonds in all his combinations.

The rest of the group will form bonds with intermediate nature between covalent and ions bods in their respective compounds, with thallium (Tl) behaving most close to a metal.

Moreover boron have a very high melting points (around 2200 °C) while in the boron cristal the chemical bonds are directed in space, similar with carbon suggesting his nature as a non-metal.

Other elements form the group Al, Ga, In, Tl have lower melting points 660, 30, 157 and 304 °C, respectively. Also in the elemental state, they have metallic characteristics: metalic luster, ductility, high electrical and thermal conductivity.

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3 years ago

Sodium chloride (NaCl) is commonly used to melt ice on roads during the winter. Calcium chloride (CaCl2) is sometimes used for t

mihalych1998 [28]

Answer:

$\Delta Tfp_{NaCl}= -14.0\°C\\\\\Delta Tfp_{CaCl_2}=-11.1\°C$

Explanation:

Hello!

In this case, since the freezing point depression caused by the addition of a solute, we use the following formula:

$\Delta Tfp= i*m*Kfp$

Thus, we first need to compute the molality of each solute, as shown below:

$m_{NaCl}=\frac{220.g/(58.44g/mol)}{1.00kg} =3.76m\\\\m_{CaCl_2}=\frac{220.g/(110.98g/mol)}{1.00kg} =1.98m$

Next, since NaCl has two ionic species, one Na⁺ and one Cl⁻, and CaCl₂ three, one Ca²⁺ and two Cl⁻, the van't Hoff's factors are 2 and 3 respectively, therefore the freezing point depressions turn out:

$\Delta Tfp_{NaCl}= 2*3.76m*-1.86\°C/m=-14.0\°C\\\\\Delta Tfp_{CaCl_2}= 3*1.98m*-1.86\°C/m=-11.1\°C$