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3 years ago

Please help urgent !!! How does an instant cold pack get cold so quickly?

Chemistry

2 answers:

strojnjashka [21]3 years ago

4 0

Answer: it has ice in it and that makes the things you use with the cold pack colder

Anon25 [30]3 years ago

3 0

Answer:

When the inner bag of water is broken by squeezing the package, it dissolves the solid in an endothermic reaction. This reaction absorbs heat from the surroundings, quickly lowering the pack's temperature.

Explanation:

Uh, yea.

Have a good day!

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A 3.140 molal solution of NaCl is prepared. How many grams of NaCl are present in a sample containing 2.692 kg of water

S_A_V [24]

Answer:

494.49 g of NaCl.

Explanation:

Data obtained from the question include the following:

Molality of NaCl = 3.140 m

Mass of water = 2.692 kg

Mass of NaCl =.?

Next, we shall determine the number of mole of NaCl in the solution.

Molality is simply defined as the mole of solute per unit kilogram of solvent. Mathematically, it is expressed as

Molality = mole of solute /Kg of solvent

With the above formula, we can obtain the number of mole NaCl in the solution as follow:

Molality of NaCl = 3.140 m

Mass of water = 2.692 kg

Mole of NaCl =..?

Molality = mole of solute /Kg of solvent

3.140 = mole of NaCl /2.692

Cross multiply

Mole of NaCl = 3.140 x 2.692

Mole of NaCl = 8.45288 moles

Finally, we shall covert 8.45288 moles of NaCl to grams. This can be obtained as follow:

Mole of NaCl = 8.45288 moles

Molar mass of NaCl = 23 + 35.5 = 58.5 g/mol

Mass of NaCl =.?

Mole = mass /Molar mass

8.45288 = mass of NaCl /58.5

Cross multiply

Mass of NaCl = 8.45288 × 58.5

Mass of NaCl = 494.49 g.

Therefore, 494.49 g of NaCl are present in the solution.

8 0

3 years ago

A covalent bond in which electrons are shared unequally is

tekilochka [14]

Covalent bonds = sharing of electrons between two atoms of the same elements or elements close to each other on the periodic table. Usually they are metals sometimes non-metals. In polar bonds electrons are shared unequally. Non polar bonds share electrons equally.

7 0

3 years ago

Under identical conditions, separate samples of O2 and an unknown gas were allowed to effuse through identical membranes simulta

Vilka [71]

Answer:

147.2g

Explanation:

The full solution can be found in the image attached. Graham's law was applied to the problem. The rate of diffusion of a gas is inversely proportional to its molar mass or vapour density. Molar mass= 2vapour density

8 0

3 years ago

AUG, the codon that codes for the amino acid methionine is also called a ____ codon (answer choices 1.start 2.Stop 3.Go 4.beginn

Katarina [22]

<h2>Answer: START (2)</h2>

Explanation:

AUG is a <u>START</u> codon. (2)

A start codon is the first codon translated by a ribosome. It usually produces an amino acid that initiates the producyion of a polypeptide chain.

5 0

3 years ago

Which of these is an isoelectronic series? 1) na+, k+, rb+, cs+ 2) k+, ca2+, or, s2– 3) na+, mg2+, s2–, cl– 4) li, be, b, c 5) n

ss7ja [257]

An isoelectronic series is where all of the ions listed have the same number of electrons in their atoms. When an atom has net charge of zero or neutral, it has equal number of protons and electrons. Hence, it means that the atomic number = no. of protons = no. of electrons. If these atoms become ions, they gain a net charge of + or -. Positive ions are cations. This means that they readily GIVE UP electrons, whereas negative ions (anions) readily ACCEPT electrons. So, to know which of these are isoelectronic, let's establish first the number of electron in a neutral atom from the periodic table:

Na=11; K=19; Rb=37; Cs = 55; Ca=20; S=16; Mg=12; Li=3; Be=4; B=5; C=6

A. Na⁺: 11-1 = 10 electrons
K⁺: 19 - 1 = 18 electrons
Rb⁺: 37-1 = 36 electrons

B. K⁺: 19 - 1 = 18 electrons
Ca²⁺: 20 - 2 = 18 electrons
S²⁻: 16 +2 = 18 electrons

C. Na⁺: 11-1 = 10 electrons
Mg²⁺: 12 - 2 = 10 electrons
S²⁻: 16 +2 = 18 electrons

D. Li=3 electrons
Be=4 electrons
B=5 electrons
C=6 electrons

The answer is letter B.

7 0

4 years ago