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3 years ago

Using the words cohesive and adhesive, explain why water forms a meniscus?

1 answer:

3 0

Adhesion is responsible for a meniscus and this has to do in part with water's fairly high surface tension. Water molecules are attracted to the molecules in the wall of the glass beaker. And since water molecules like to stick together, when the molecules touching the glass cling to it, other water molecules cling to the molecules touching the glass, forming the meniscus. They'll travel up the glass as far as water's cohesive forces will allow them, until gravity prevents them from going further. Cohesion is an intermolecular attraction between like molecules (other water molecules in this case).

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The value of Kp for the reaction NO(g) 1 1 2 O2(g) 4 NO2(g) is 1.5 3 106 at 25°C. At equilibrium, what is the ratio of PNO2 to P

expeople1 [14]

Answer : The ratio of $p_{NO_2}$ to $p_{NO}$ is, $6.87\times 10^5$

Solution : Given,

$K_p=1.5\times 10^6$

$p_{O_2}$ = 0.21 atm

The given equilibrium reaction is,

$NO(g)+\frac{1}{2}O_2\rightleftharpoons NO_2(g)$

The expression of $K_p$ will be,

$K_p=\frac{(p_{NO_2})}{(p_{NO})\times (p_{O_2})^{\frac{1}{2}}}$

Now put all the given values in this expression, we get:

$1.5\times 10^6=\frac{(p_{NO_2})}{(p_{NO})\times (0.21)^{\frac{1}{2}}}$

$\frac{(p_{NO_2})}{(p_{NO})}=(1.5\times 10^6)\times (0.21)^{\frac{1}{2}}$

$\frac{(p_{NO_2})}{(p_{NO})}=6.87\times 10^5$

Therefore, the ratio of $p_{NO_2}$ to $p_{NO}$ is, $6.87\times 10^5$

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3 years ago

What holds the two strands of a DNA molecule together?A. Ionic bonds between negatively and positively charged ionsB. Covalent b

statuscvo [17]

Answer:

D. Hydrogen bonds between complementary base pairs89

Explanation:

A DNA molecule is composed of two long polynucleotide chains made of four types of nucleotide subunits, two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). These nucleotides are joined by covalent bonds forming a phosphate-sugar backbone. These strands are held to one another with hydrogen bonds between the base portions of complementary nucleotides.

I hope you find this information useful and interesting! Good luck!

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3 years ago

What is the empirical formula of C6H12O6? C2H4O2 CH2O CH2O2 C2H4O

wariber [46]

Answer: The empirical formula for C6H12O6 is CH2O. Every carbohydrate, be it simple or complex, has an empirical formula CH2O

Explanation:

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2 years ago

3,010,000 into scientific notation

skelet666 [1.2K]

Answer:

3.01 x 10 to the power of 6

Explanation:

Step 1

To find a, take the number and move a decimal place to the right one position.

Original Number: 3,010,000

New Number: 3.010000

Step 2

Now, to find b, count how many places to the right of the decimal.

3 0

3 years ago

Read 2 more answers

Any help would be appreciated. Confused.

masya89 [10]

Answer:

q(problem 1) = 25,050 joules; q(problem 2) = 4.52 x 10⁶ joules

Explanation:

To understand these type problems one needs to go through a simple set of calculations relating to the 'HEATING CURVE OF WATER'. That is, consider the following problem ...

=> Calculate the total amount of heat needed to convert 10g ice at -10°C to steam at 110°C. Given are the following constants:

Heat of fusion (ΔHₓ) = 80 cal/gram

Heat of vaporization (ΔHv) = 540 cal/gram

specific heat of ice [c(i)] = 0.50 cal/gram·°C

specific heat of water [c(w)] = 1.00 cal/gram·°C

specific heat of steam [c(s)] = 0.48 cal/gram·°C

Now, the problem calculates the heat flow in each of five (5) phase transition regions based on the heating curve of water (see attached graph below this post) ... Note two types of regions (1) regions of increasing slopes use q = mcΔT and (2) regions of zero slopes use q = m·ΔH.

q(warming ice) = m·c(i)·ΔT = (10g)(0.50 cal/g°C)(10°C) = 50 cal

q(melting) = m·ΔHₓ = (10g)(80cal/g) 800 cal

q(warming water) = m·c(w)·ΔT = (10g)(1.00 cal/g°C)(100°C) = 1000 cal

q(evaporation of water) = m·ΔHv = (10g)(540cal/g) = 5400 cal

q(heating steam) = m·c(s)·ΔT = (10g)(0.48 cal/g°C)(10°C) = 48 cal

Q(total) = ∑q = (50 + 800 + 1000 + 5400 + 48) = 7298 cals. => to convert to joules, multiply by 4.184 j/cal => q = 7298 cals x 4.184 j/cal = 30,534 joules = 30.5 Kj.

Now, for the problems in your post ... they represent fragments of the above problem. All you need to do is decide if the problem contains a temperature change (use q = m·c·ΔT) or does NOT contain a temperature change (use q = m·ΔH).

Problem 1: Given Heat of Fusion of Water = 334 j/g, determine heat needed to melt 75g ice.

Since this is a phase transition (melting), NO temperature change occurs; use q = m·ΔHₓ = (75g)(334 j/g) = 25,050 joules.

Problem 2: Given Heat of Vaporization = 2260 j/g; determine the amount of heat needed to boil to vapor 2 Liters water ( = 2000 grams water ).

Since this is a phase transition (boiling = evaporation), NO temperature change occurs; use q = m·ΔHf = (2000g)(2260 j/g) = 4,520,000 joules = 4.52 x 10⁶ joules.

Problems containing a temperature change:

NOTE: A specific temperature change will be evident in the context of problems containing temperature change => use q = m·c·ΔT. Such is associated with the increasing slope regions of the heating curve. Good luck on your efforts. Doc :-)

5 0

3 years ago

Using the words cohesive and adhesive, explain why water forms a meniscus?​

Using the words cohesive and adhesive, explain why water forms a meniscus?