help now plsss I really need help !!!!

Answer:

B. The temperature of the water when the food sample has finished burning completely.

Explanation:

Heat or thermal energy is a form of energy that transfers from one object to another due to a temperature difference between the objects. The units for heat are joules or calories.

Calorimetry is the measurement of heat energy released or absorbed in a chemical  reaction. A calorimeter is used in calorimetry. The calorimeter operates on the Law of Conservation of Energy which states that energy is never created or destroyed but is transformed from one form to another or between objects.

In food calorimetry, the energy released when food is burned is measured by recording the rise in temperature of water in a calorimeter when a given mass of a food sample is burned completely.

Energy can be calculated using the formula: Q = mc ∆T

where Q = the energy in joules or calories, m = the mass in grams, c = specific heat and ∆T = the change in temperature (final temperature - initial temperature).

The temperature of the water when the food sample has finished burning completely is taken as the final temperature of the water. The sample is allowed to smolder for sometime before recording the final  water temperature. This is because the water temperature will continue to rise after the  flame has gone out.

Answer:

Yes, 0.11g/mL is the solubility of X in water at 17.0°C.

Explanation:

As the sample of water has crystals around it, the solution is oversaturated at 17.0°C. The water contains the maximum amount of X at 17.0°C, this concentration is called solubility. Thus, yes, we can calculate solubility in water at 17.0°C

The concentration of the crystals is 3.96g in 36.0mL, that is:

3.96g / 36.0mL =

Answer:

1.  ¹⁰₄Be ---> ¹⁰₅B + ⁰₋₁β

2. ³⁴₁₄Be ---> ³⁴₁₅P + ⁰₋₁β

3. ¹⁹²₇₈Pt -----> ¹⁹⁰₇₆Os + ⁴₂α

4.  ²⁸₁₂Mg ---> ²⁸₁₃Al + ⁰₋₁β

Explanation:

1. In the first equation, Beryllium-10 isotope undergoes beta-decay, emitting a beta-particle to form boron-10 isotope. The balanced nuclear equation is given below:

¹⁰₄Be ---> ¹⁰₅B + ⁰₋₁β

2. In this reaction, silicon-34 isotope undergoes beta-decay, emitting a beta-particle to form phosphorus-34 isotope. The balanced nuclear equation is given below:

³⁴₁₄Be ---> ³⁴₁₅P + ⁰₋₁β

3. In this equation, platinum-192 isotope undergoes alpha-particle decay emitting an alpha-particle to form osmium-190 isotope. The balanced nuclear equation is given below:

¹⁹²₇₈Pt -----> ¹⁹⁰₇₆Os + ⁴₂α

4. In this equation, magnesium-28 isotope undergoes beta-decay, emitting a beta-particle to form aluminum-28 isotope. The balanced nuclear equation is given below:

²⁸₁₂Mg ---> ²⁸₁₃Al + ⁰₋₁β

Chemical Changes

Chemical changes take place at the molecular level. A chemical change produces a new substance. Another way to think of it is that a chemical change accompanies a chemical reaction. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.

Physical Changes

Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance, although the starting and ending materials may look very different from each other. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.

How to Tell Chemical & Physical Changes Apart

A chemical change makes a substance that wasn't there before. There may be clues that a chemical reaction took places, such as light, heat, color change, gas production, odor, or sound. The starting and ending materials of a physical change are the same, even though they may look different.

hope this helps

5 star and brainliest?

Answer:

C)Grassland biomes contain mostly grasses.

Explanation:

The main differences between a savanna biome and a grassland is that grasslands biomes contain mostly grasses.

Savanna are made up of both grasses and shrubs.

Answer:

C. Plate tectonic collisions can create mountains.

Answer:

They can make them larger

Explanation:

They go up under a mountain and then the mountains rise up

Answer:

This indicates there will be the densest (heaviest) liquid on the bottom of the jar there will be the least dense (lightest) liquid on top. Syrup, glycerin, water, oil, and then alcohol would be on top of the order of liquids from hardest to lightest.

Answer:

Explanation:

From the given information:

The compound in question here is [tex]\mathbf{C_2H_5Br}[/tex]

The molar mass of [tex]\mathbf{C_2H_5Br}[/tex] with 79 Br  is;

= (2 × 12) + (1 × 5) + 79

= 108 g/mol

The molar mass of [tex]\mathbf{C_2H_5Br}[/tex] with 81 Br is:

=  (2 × 12) + (1 × 5) + 81

= 110 g/mol

Thus, the mass at which the molecular ions occurs are:

108 and 110.

The relative percentage of mass 108 occurred at 50.7%

The relative percentage of mass 110 occurred at 49.3%

Answer:

25 mM Tris HCl and 0.1% w/v SDS

Explanation:

A 10X solution is ten times more concentrated than a 1X solution. The stock solution is generally more concentrated (10X) and for its use, a dilution is required. Thus, to prepare a buffer 1X from a 10X buffer, you have to perform a dilution in a factor of 10 (1 volume of 10X solution is taken and mixed with 9 volumes of water). In consequence, all the concentrations of the components are diluted 10 times. To calculate the final concentration of each component in the 1X solution, we simply divide the concentration into 10:

(250 mM Tris HCl)/10 = 25 mM Tris HCl

(1.92 M glycine)/10 = 0.192 M glycine

(1% w/v SDS)/10 = 0.1% w/v SDS

Therefore the final concentrations of Tris and SDS are 25 mM and 0.1% w/v, respectively.

Answer:

Explanation:

here's the answer hope it helps! :)

Answer:

iconic bond is the answer

I hope it helps you ✌

Answer:

An ionic bond is the electrostatic force that holds ions together when they form bonds

Explanation:

An ionic bond is formed when a metal looses electron(s) to a non metal leading to the formation of a positive ion and a negative ion.

An ionic compound is actually an ion pair, the ions are held together by strong electrostatic forces.

This strong electrostatic force that holds the ion pair together in ionic compounds is what we commonly call the IONIC BOND.  

Answer:

An ionic bond is the electrostatic force that holds ions together when they form bonds

Explanation:

I took this test and it was the correct answer :)

The number of Hydrogen atoms = 6 atoms

Given

Reaction

N₂ + 3H₂ ⇒ 2NH₃

Required

The number of Hydrogen atoms

Solution

The reaction coefficient of a chemical equation shows the mole ratio of the reacting compound.

On a compound the reaction coefficient indicates the number of molecules

Whereas the subscript after the atom shows the number of atoms in that compound

Product from the reaction : 2NH₃

Number of H-atoms :

= 2 x 3

= 6 atoms

Answer:

I don't get it is it even a question?

Answer:

257 mL

Explanation:

Step 1: Given data

Step 2: Calculate the moles (n) corresponding to 32.8 g of HCl

The molar mass of HCl is 36.46 g/mol.

32.8 g × 1 mol/36.46 g = 0.900 mol

Step 3: Calculate the volume (V) of solution required

We will use the following expression.

C = n/V

V = n/C

V = 0.900 mol/(3.50 mol/L)

V = 0.257 L = 257 mL

Answer:

Fluorine (F)

Explanation:

The poorest conductor of electricity from the given choices is fluorine. This is because fluorine is a non - metal.

Like other non - metals, fluorine does not conduct electricity.

Only metals are known to conduct electricity and heat readily.

Semi - metals like silicon will conduct electricity under specific condition.

The free mobile electrons in metals makes it easy for them propagate electricity

Answer:

C

Explanation:

0.10 moles of Fe[tex]_2[/tex]O[tex]_3[/tex]  are in 17.2g. Therefore, the correct option is option D among all the given options.

The inorganic chemical with both the formula Fe[tex]_2[/tex]O[tex]_3[/tex] is iron(III) oxide and ferric oxide. It is one of three major iron oxides, the other 2 including iron(II) oxide (FeO), which would be uncommon, and iron(II,III) oxides (Fe[tex]_2[/tex]O[tex]_3[/tex]), which naturally occurs as the mineral magnetite. 

Acids have a high affinity for Fe[tex]_2[/tex]O[tex]_3[/tex] . Iron(III) oxide is commonly referred to as rust, and this name is appropriate to some extent because rust has certain features and has a comparable composition; nevertheless, in chemistry, colouration is classified under Hydrous ferric oxide.

mole =  17.2/ 159.69 =0.10moles

Therefore, the correct option is option D.

To know more about iron(III) oxide, here:

https://brainly.com/question/8834237

#SPJ2

Answer:

0.48g

Explanation:

Given parameters:

Mass of zinc  = 15g

Unknown:

Mass of hydrogen gas = ?

Solution:

To solve this problem, we need to state the balanced reaction expression first;

          Zn   +   2HCl   →   ZnCl₂    +   H₂

Find the number of moles of Zn;

    Number of moles  = [tex]\frac{mass}{molar mass}[/tex]    = [tex]\frac{15}{63.4}[/tex]    = 0.24mol

From the balanced reaction expression;

             1 mole of Zn will produce 1 mole of H₂  

            0.24mole of Zn will produce 0.24mole of hydrogen gas

Mass of hydrogen gas  = number of moles x molar mass

                                      = 0.24 x (2 x 1)

                                      = 0.48g

This question is incomplete, the complete question is;

Consider this reaction:

2H₃PO₄(aq) → p₂o₅(aq) + 3H₂O(aq)

At a certain temperature it obeys this rate law.

rate = ( 46.65 M⁻¹.s⁻¹) [ H₃PO₄ ]²

Suppose a vessel contains H₃PO₄  at a concentration of 0.660 M .

Calculate how long it takes for the concentration of H₃PO₄  to decrease  to 20.0% of its initial value .

You may assume no other reaction is important.

Round your answer to significant digits.

Answer:

time taken is 8.574 × 10⁻⁴ s

Explanation:

Given that;

rate = k[ H₃PO₄ ]²

rate constant k = 46.65 M⁻¹.s⁻¹)

Initial concentration A₀ =  0.660 M { which will be 100%}

final concentration At = 20%

for the concentration of H₃PO₄  to decrease  to 20.0% of its initial value = ?

we know that;

rate constant k =  1/t [ 1/At - 1/A₀ ]

we substitute

46.65 = 1/t [ 1/20 - 1/100 ]

46.65 = 1/t [ 0.04 ]

46.65 = 0.04/t

46.65t = 0.04

t = 0.04 / 46.65

t = 0.0008574  ≈ 8.574 × 10⁻⁴ s

Therefore, time taken is 8.574 × 10⁻⁴ s

Answer:

predator

Explanation:

Wolves, arctic foxes, and snowy owls are predators in the tundra.

Answer:

V = 0.03735 mL

Explanation:

Given that,

Mass of a substance, m = 88.9 grams

Density of a substance, d = 2.38 g/mL

We need to find the volume occupied by the object. The density of an object is given by mass per unit volume.

[tex]d=\dfrac{m}{V}\\\\V=\dfrac{m}{d}\\\\V=\dfrac{88.9}{2.38}\\\\V=37.35\ mL\\\\V=0.03735\ L[/tex]

So, the volume of the substance is 0.03735 mL.

Answer:

1. B 2.B

Explanation:

Answer:

32.7 g

Explanation:

Step 1: Write the balanced combustion reaction

C₄H₁₀ + 6.5 O₂ ⇒ 4 CO₂ + 5 H₂O

Step 2: Calculate the moles corresponding to 99.0 g of CO₂

The molar mass of CO₂ is 44.01 g/mol.

99.0 g × 1 mol/44.01 g = 2.25 mol

Step 3: Calculate the moles of C₄H₁₀ needed to produce 2.25 moles of CO₂

The molar ratio of C₄H₁₀ to CO₂ is 1:4. The moles of C₄H₁₀ needed are 1/4 × 2.25 mol = 0.563 mol.

Step 4: Calculate the mass corresponding to 0.563 moles of C₄H₁₀

The molar mass of C₄H₁₀ is 58.12 g/mol.

0.563 mol × 58.12 g/mol = 32.7 g

Answer:

$4.49 g/cm3

Explanation:

Density=Mass/Volume

plzz put brainiest

Answer: suspensions  are a mixture in which solute particles do not disolve. An example is oil and water, oil and water or even flour and water; oil can’t disolve in water

Answer:

Noun: a mixture in which particles are dispersed throughout the bulk of a fluid.

Adjective: the state of being dispersed in a fluid.

Explanation:

I used a dictionary lol

Answer:

Ba(OH)2 + H2SO3 = BaSO3 + H2O -

Explanation:

Answer:

3.39x10⁻⁹ M

Explanation:

Let's assume we have 1 mL of the stream. With a density of 1.0 g/mL, we would have 1 g of the stream.

Now we calculate the mass of mercury present in 1 g of the stream, using its given concentration (0.68 ppb):

Now we convert that mass into moles, using mercury's atomic mass:

Finally we calculate the molarity of mercury, as we know that there are 3.39x10⁻¹² Hg moles in 1 mL of the stream:

Answer:

[tex]PtCl_4[/tex]

Explanation:

Hello!

In this case, since HCl and Pt react according to the following chemical equation:

[tex]HCl+Pt\rightarrow PtCl_x+H_2[/tex]

Whereas PtClx is the compound containing Pt and Cl; thus, since 1.018 g out of 1.778 g correspond to Pt and therefore 0.760 g to chlorine, so we determine the empirical formula of this compound by firstly computing the moles of each element:

[tex]n_{Pt}=1.018gPt*\frac{1molPt}{195.084gPt}=0.00522molPt\\\\\\n_{Cl}=0.760gCl*\frac{1molCl}{35.45gCl} =0.0214molCl[/tex]

Now, we divide the each moles by those of Pt as the fewest ones in order to compute their subscripts in the empirical formula:

[tex]Pt=\frac{0.00522}{0.00522}=1 \\\\Cl=\frac{0.0214}{0.00522} =4[/tex]

Thus, the required formula is:

[tex]PtCl_4[/tex]

Best regards!