How many moles of molecular oxygen will be needed for the complete combustion of 100.0 g of sulfur dioxide? The product of this reaction is sulfur trioxide

Answers

Answer 1

Answer:

0.78 mol O2

Explanation:

2SO2 + O2  -> 2 SO3

64 g SO2  -> 1 mol SO2

100 g SO2 -> x

x= (100 g SO2 * 1 mol SO2)/64 g SO2     x=1.56 mol SO2

1 mol O2 -> 2 mol SO2

         x    -> 1.56 mol SO2

x= (1.56 mol SO2 * 1 mol O2)/2 mol SO2          x=0.78 mol O2

Answer 2

Answer:

0.7804

Explanation:


Related Questions

What is the atomic number of this atom?

Answers

Answer:

2?????

Explanation:

The atomic number is b

1.
What is light energy converted from in the bulb of a lamp?


electric energy
sound energy
heat energy
2.
Which is the best example of an object that converts electric energy to heat energy?


lamp
toaster
radio
3.
Which is evidence of electric energy converted to sound energy?


music heard from a radio
a song played on a piano
applause from an audience

Answers

1) electric energy

2) toaster

3) music heard from a radio

Answer:

1.Electrical energy

2. Toaster

3. Music heard from a radio

According to Boyle's law, how would you reduce the volume of a gas?

a. by decreasing its pressure
b. by increasing its temperature
c. by decreasing its temperature
d. by increasing its pressure

Answers

Answer:

by increasing pressure

Explanation:

volume is inversely proportional to pressure at constant temperature

Answer:

d. Increasing the pressure.

Explanation:

Boyle's law state that P*  V is constant at a given temperature.

So to reduce the volume you would increase the pressure.

The sugar deoxyribose is an important component of DNA. Deoxyribose is 44.8% 7.5% H, and 47.7% O by mass. What is the empirical formula for deoxyribose?

Answers

Answer:

C₅H₁₀O₄  

Explanation:

The empirical formula is the simplest whole-number ratio of atoms in a compound.

The ratio of atoms is the same as the ratio of moles.

So, our job is to calculate the molar ratio of C:H:O.

Assume 100 g of deoxyribose.

1. Calculate the mass of each element.

Then we have 44.8 g C, 7.5 g H, and 47.7 g O.

2. Calculate the moles of each element

[tex]\text{Moles of C} = \text{44.8 g C} \times \dfrac{\text{1 mol C}}{\text{12.01 g C}} = \text{3.730 mol C}\\\\\text{Moles of H} = \text{7.5 g H} \times \dfrac{\text{1 mol H}}{\text{1.008 g H }} = \text{7.44 mol H}\\\\\text{Moles of O} = \text{47.7 g O} \times \dfrac{\text{1 mol O}}{\text{16.00 g O }} = \text{2.981 mol O}[/tex]

3. Calculate the molar ratio of the elements

Divide each number by the smallest number of moles

C:H:O = 3.730:7.44:2.981 = 1.251:2.50:1 = 5.005:9.98:4 ≈ 5:10:4

4. Write the empirical formula

EF = C₅H₁₀O₄


How many grams are in 0.25 mol KNO3? The molar mass of KNO3 is 101 g/mol.

Answers

Answer: 25.3g

Explanation:

The number of moles in chemistry is connected to the Mass and Molar mass of a compond through the following formular;

Moles = Mass (g)  /  Molar Mass (g/mol)

0.25 mol  =  Mass (g) / 101 g/mol

Make 'Mass' the subject of the formular;

Mass = 0.25 mol x 101 g/mol

          = 25.25 approx 25.3g

Predict what would happen inside the magnet if the magnet were to break in half

Answers

if a magnet were to break in half, the new pieces would each get their own positive and negative sides just like the original magnet
Magnets are kinda like batteries. If you cut a magnet in half, the newly cut faces will into smaller positive and negative pieces. So technically it’ll become smaller with a weaker magnetic pull.

Explain why floods, hurricanes, and tornadoes are aspects of weather, not climate.

Answers

Answer:

Floods, hurricanes, and tornadoes are all aspects of weather and not climate because climate is more related to temperature. The definition of climate is "the weather conditions prevailing in an area in general or over a long period." Floods, hurricanes, and tornadoes are not aspects of climate, they are aspects of weather.

Explanation:

Floods, hurricanes, and tornadoes are considered weather events due to their immediate and short-term nature, while climate refers to the long-term average weather patterns in a region. Weather involves day-to-day atmospheric conditions, leading to various forms of severe weather, whereas climate encompasses the general weather trends and conditions over a prolonged period.

Floods, hurricanes, and tornadoes are categorized as aspects of weather rather than climate due to their short-term occurrence and direct impact on specific regions over a brief period. Weather involves immediate atmospheric conditions, such as precipitation, wind speeds, and temperature, which can lead to the development of these extreme weather events. In contrast, climate describes the average weather conditions in a particular area over a long period, typically years or decades, encompassing patterns and trends rather than individual or short-term events. For instance, the differential heating of the Earth's surface by the Sun, which significantly influences weather patterns, can lead to the formation of severe weather phenomena like tornadoes, characterized by their funnel-shaped clouds and powerful winds, and hurricanes, known for their high winds and heavy rains forming over warm ocean waters.

The distinction between weather and climate is crucial for understanding how external forces like the Sun's heating influence Earth's atmospheric conditions, leading to immediate weather conditions and longer-term climatic trends. While floods, hurricanes, and tornadoes manifest as a result of these conditions, representing the variability and extremity of weather, climate refers to the broader, more consistent patterns that define a region's average atmospheric conditions over time.

Select the phrase that completes each statement.
Honey is
Grape juice is
Sand on the beach is
• A mixture of carbon dioxide and nitrogen
gases is

Rubbing alcohol is

Answers

Answer:

1) A mixture and a solution.

2) A mixture and a solution.

3) A mixture but not a solution.

4) A mixture and a solution.

5) A mixture and a solution.

Explanation:

Honey, grape juice, a mixture of carbon dioxide and nitrogen gases, and rubbing alcohol are homogeneous mixtures, while sand on the beach is a heterogeneous mixture.

To complete the statements accurately, let's classify each substance:

Honey is a homogeneous mixture (solution) - It is a uniform mixture of water, sugars, and other compounds.

Grape juice is a homogeneous mixture (solution) - It contains water, sugars, acids, and other dissolved compounds that appear uniform throughout.

Sand on the beach is a heterogeneous mixture - It consists of different particles such as quartz, shells, and organic matter that are not uniform throughout.

A mixture of carbon dioxide and nitrogen gases is a homogeneous mixture (solution) - It forms a uniform gaseous mixture.

Rubbing alcohol is a homogeneous mixture (solution) - It is typically a mixture of isopropanol and water, appearing uniform throughout.

to prepare 100 mL of a 0.5 M solution of CuSO4 using water as the solvent. Calculate the amount of solid needed.

Answers

Answer:

Explanation:

100 mL of a .5 M solution

= 0.1 L of .5 M solution

This solution will contain .1 x .5 mole of solute

= .05 mole of solute

molecular weight of CuSO₄

= 63.5 + 32 + 64

= 159.5 gm

one mole of CuSO₄  = 159.5 gm

.05 mole = 159.5 x .05 gm

= 7.975 gm

7.975 gm of CuSO₄ will be required .

The image below shows the surface of the Moon.


The circle-shaped pits on the surface of the Moon are usually caused by collisions with asteroids or comets and are known as _______.
A.
plains
B.
mountains
C.
dunes
D.
craters

Answers

The answer is D
Hope this helps !
The answer is craters hope that help:)

What is the rate of a reaction if the values are
k=0.1
a=1 M
b=2 M

rate=k(a)^2(b)^2

Answers

Answer:

Explanation:

Hi there,

To get started, let's first observe our rate law:

[tex]R=k[A]^2[B]^2[/tex]     we typically use square brackets [x] for chemistry kinetics, because they specifically tell us we are dealing with concentrations.

This rate law is in fourth-order, because the concentrations powers add up to 4. We are not told the unit of time for this prompt (unless you know it), so I just assumed the time unit to be "time."

To calculate the reaction rate, we simply plug in the concentration of A and B into the rate law. k is the rate constant and stays the same for an individual reaction.

[tex]R=(0.1 \ M^{-3}*time^{-1})[1 \ M]^2[2 \ M]^2=0.4 \ M/time[/tex]

Thus, the rate of reaction with those concentrations is 0.4 M/time.

Notice, the rate constant does in fact have units of it own. The unit for k can be calculated by knowing that:

Rate (R) must end up with units of concentration (M) per time. The concentrations raised to a power can be used to help solve for the units of k.

If you liked this solution, leave it as Brainliest Answer and give a Rating!

The rate of reaction with those concentrations is 0.4 M/time.

What is the rate of a reaction?

The reaction rate is said to be the decrease in the concentration of the reactant or the increase in the concentration of the product per unit of time. Reaction rate measures how fast the reactant is used up or how fast the product is formed.

For a given reaction like

[tex]Mg(s) + O_2(g)[/tex] → [tex]2MgO(aq)[/tex]

The reaction rate is derived by measuring how fast the concentration of Mg and [tex]O_2[/tex] decreases or how fast the concentration of MgO increases. Mathematically reaction rate can be expressed as

Reaction rate = Δconcentration/ ΔTime

Rate=[tex]k(a)^2(b)^2[/tex] We typically use square brackets [x] for chemistry kinetics, because they specifically tell us we are dealing with concentrations.

This rate law is in fourth-order because the concentration powers add up to 4. We are not told the unit of time for this prompt (unless you know it), so I just assumed the time unit to be "time."

To calculate the reaction rate, we simply plug the concentration of A and B into the rate law. k is the rate constant and stays the same for an individual reaction.

Thus, the rate of reaction with those concentrations is 0.4 M/time.

Learn more about the rate of reaction here:

https://brainly.com/question/15766136

#SPJ5

5.
To inflate a weather balloon you must increase its volume from 0.58 L (nearly empty for a weather balloon) to a full volume
against an external pressure of 1 atm exactly. The process requires 22.632 kJ of work. What is the volume of the balloon?

(The original formula would be something around [deltaE = deltaH - PdeltaV])

Answers

Answer:

ANswers is simply

Explanation:

8.73kJ

If 0.04625 mg. of Uranium-235 remains after 2.8 x 10^9 years, what was
the original mass of the sample of Uranium-235? The half-life of Uranium-235 is 7.0 x 10^8 years.

Answers

Answer: The original mass of the sample of Uranium-235 is 0.7308 mg

Explanation:

Expression for rate law for first order kinetics is given by:

[tex]t=\frac{2.303}{k}\log\frac{a}{a-x}[/tex]

where,

k = rate constant

t = age of sample

a = let initial amount of the reactant

a - x = amount left after decay process  

a) for calculating rate constant

[tex]t_{\frac{1}{2}}=\frac{0.693}{k}[/tex]

[tex]k=\frac{0.693}{7.0\times 10^8years}=0.099\times 10^{-8}years^{-1}[/tex]

b) for time of [tex]2.8\times 10^9[/tex] years

[tex]2.8\times 10^9=\frac{2.303}{0.099\times 10^{-8}}\log\frac{a}{0.04625}[/tex]

[tex]\log\frac{a}{0.04625}=1.2[/tex]

[tex]\frac{a}{0.04625}=15.8[/tex]

[tex]a=0.7308mg[/tex]

The original mass of the sample of Uranium-235 is 0.7308 mg

Using your knowledge of wave characteristics and energy conversions, explain how musicians create, record, store, and replay analog sounds.

Answers

Answer:

In creating music, sound waves from the singer in the form of vibrational energy strikes and is converted into electrical signals in the microphone.

These electrical signals are converted to a magnetic field and then stored on an analogue recorder in the form of magnetic domains.

When the song is replayed, these magnetic domains create a changing magnetic field which produces electrical signal.

The electrical signal is sent to the voice coil in the speaker, where it is converted to a magnetic field.

The changing magnetic field pulls and push on the diaphragm which sets the air around it into vibration.

This vibration becomes sound wave that strikes our ears when we listen to these sounds.

A reaction occurs when solid X is placed into solution Y. As a result, the temperature of the new solution increases by 3°C.
The temperature rises another 2°C when more of solid X is added to the solution. What does this indicate about the effect of
adding more solid?
It increased the number of molecular collisions.
It decreased the number of molecular collisions.
It decreased the space between the molecules and lowered the reaction rate.
It increased the space between the molecules and increased the reaction rate.
Mark this and return
Save and Exit
Next
Submit

Answers

It increases the number of molecular collisions.

How does wavelength differ in high and low frequency waves?

Answers

Waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths

In high frequency waves, the wavelength is short and appears in many short bursts. Meanwhile, in a low frequency wave, the wavelength is longer since it takes it a longer period of time to occur/pass.

At the extreme temperatures within the Sun, hydrogen forms plasma. Plasma forms when:

1. atoms join together in chemical reactions
2. protons and electrons fuse together
3. protons fuse together, releasing heat and light
4. atoms break down to form free protons and electrons

If you could please let me know which option would be the answer to the question, it would be great!

Answers

Answer:

What do you need help with

Explanation:

Plasma forms when atoms break down to form free protons and electrons (option 4)

What is plasma?

Plasma is the fourth state of matter, after solids, liquids, and gases. It is characterized by the presence of a significant portion of charged particles in any combination of ions or electrons.

It is the most abundant form of ordinary matter in the universe, mostly in stars (including the Sun), but also dominating the rarefied intracluster medium and intergalactic medium. Plasma can be artificially generated by heating a neutral gas or subjecting it to a strong electromagnetic field.

Learn about plasma here https://brainly.com/question/950535

#SPJ3

State of Matter Chemistry TEST

The temperature of the water started rising only when:

Othere was steam coming off the water in the beaker.

Othere was only water in the beaker.

theres was ice mixed with the water in the beaker.

Answers

Answer:

Othere was steam coming off the water in the beaker.

What is the molarity of a sodium hydroxide solution if 24 mL of the solution
is titrated to the end point with 12 mL of 0.50M sulfuric acid? (Remember:
MaVa = MbVb)
•0.10M
•0.25M
•0.50M
•0.75M

Answers

Answer:

Option 3. 0.50M

Explanation:

Step 1 :

We'll begin by writing the balanced equation for the reaction. This is given below:

2NaOH + H2SO4 —> Na2SO4 + 2H2O

From the above equation, we obtained the following:

Mole ratio of the acid (nA) = 1

Mole ratio of the base (nB) = 2

Step 2:

Data obtained from the question. This includes the following:

Molarity of base (Mb) =?

Volume of base (Vb) = 24 mL

Volume of acid (Va) = 12 mL

Molarity of acid (Ma) = 0.50M

Step 3:

Determination of the molarity of the base.

The molarity of the base can be obtained by applying the following equation:

MaVa/MbVb = nA/nB

0.5 x 12/Mb x 24 = 1/2

Cross multiply to express in linear form

Mb x 24 = 0.5 x 12 x 2

Divide both side by 24

Mb = (0.5 x 12 x 2) /24

Mb = 0.5 M

Therefore, the molarity of NaOH is 0.5 M

Which change increases the electric force between objects?
O
Two neutral objects are moved closer together.
Electrons are added to two negatively charged objects.
Two oppositely charged objects are moved farther apart.
The charge on two positively charged objects is reduced.
O
O

Answers

Answer:

Electrons are added to two negatively charged objects.

Explanation:

Two negatively charged objects repel each other.

If electrons are added to two already negatively charged objects, they wil become even more negatively charged, which increases the electric force between the objects.

The electric force between objects can be increased when electrons are added to two negatively charged objects. Therefore, option B is correct.

What is electric force?

The electric force is the attraction or repulsion between electrically charged objects. The force is created by the presence of charged particles, such as electrons or protons. It is described by Coulomb's law.

Like charges repel each other, while opposite charges attract each other. The strength of the electric force depends on the amount of charge on the objects and the distance between them. The force increases as the amount of charge increases and as the distance between the objects decreases.

Electric force is a fundamental force in nature. It plays an important role in many physical phenomena, such as electricity and magnetism. Therefore, option B is correct.

Learn more about electric force, here:

https://brainly.com/question/31696602

#SPJ5

1.
Which phenomenon is responsible for sending electrically charged particles out into space?
prominences
sunspots
solar wind
O solar eclipses
w​

Answers

Answer:

solar wind

Explanation:

pls pls pls give me brainiesttt tyty

good luck :)

If you constructed graphs, what trends do they indicate in your data?

Answers

Answer:A linear pattern is a continuous decrease or increase in numbers over time. On a graph, this data appears as a straight line angled diagonally up or down (the angle may be steep or shallow). So the trend either can be upward or downward.

Explanation:

Graphs are the diagrammatic representation of the data. The constructed graph gives the upward or downward trends in the data over the respective trends.

What are the types of graphs?

The graphs can be distinguished based on the type of data representation technique used.

The graphs can be line, pie, bar, etc. The data plotted in the graph shows the trends with the angle of the line and the slope. The increasing slope tends to interpret the increasing trend, and vice versa.

Learn more about graphs, here:

https://brainly.com/question/14375099

An engineer is trying to produce as much hydrogen gas as the company can using the equipment they have.
The engineering obtained the following data from research.
Sodium + Sulfuric Acid
Sodium Sulfate + Hydrogen
Mass of Na (g)
Mass of H,SO. (g)
Mass of Na,so ()
Mass of H. (g)
1149.5
2450
3549.5
50
2299
4900
7099
100
3448.5
1
7350
10648.5
150
Beginning: (5 points)
Reacting 2299 g of sodium requires 4900 g of sulfuric acid, as seen in the data table. How many moles of each substance is
this? Show your work and/or explain the math that you used to arrive at this answer.
Developing: (5 points).
Based on the chemical equation, how much sulfuric acid, in grams, is consumed from the reaction of 1450 g of sodium
metal? Show your work and/or explain the math that you used to arrive at this answer.
Proficient: (6 points)
The equipment the engineer has can only hold a maximum of 1450 g of sodium before it is mixed with excess sulfuric acid
to carry out the reaction described above. How much hydrogen gas can be produced from the equipment they currently
have? Show your work and/or explain the math that you used to arrive at this answer.

Answers

Answer:

See explaination

Explanation:

Please kindly check attachment for the step by step solution of the given problem.

A group of scientists develops a new fertilizer. Which branch of chemistry are they engaged in?
A.) Organic Chemistry
B.) Inorganic Chemistry
C.) Biochemistry
D.) Analytical Chemistry

Answers

Answer:

A. Organic Chemistry

Explanation:

Because Fertilizer is a organic Mixture

Answer:

A. Organic Chemistry

Explanation:

When human prevent waste or loss it is known as

Answers

Answer:

im not sure exactly what terms this question is in but recycling?

How much heat is required to raise the temperature of 179g of acetic acid, CH3COOH, from 250C to 82.70C?

Answers

Answer:

HEAT REQUIRED TO RAISE THE TEMPERATURE OF 179 ACETIC ACID FROM 25 °C TO 82.7°C IS 21 100j OR 21.1 kJ

Explanation:

Heat = mcΔT

m = 179 g

C =  2.043 J.g-1K-1

ΔT = ( 82.70 - 25 ) = 57.7°C

Heat = 179 * 2.043 * 57.7

Heat = 21, 100.72 J

Heat ≅ 21.1 kJ

Which subscripts complete the chemical formula for the compound?

CaHb

Answer choices for a: 1,3,8
b:1,3,8

Answers

Question:

Which subscripts complete the chemical formula for the compound?

Answer:

A: 3

B: 8

Answer:

A) 3

B) 8

Explanation:

All living organisms are part of their environment which is composed of biotic and abiotic factors that interact with each other. The interaction of living organisms with its environment are vital to the organisms survial. What is this interaction called?

Answers

Answer:

Ecology

Explanation:

Final answer:

The term for the interaction between living organisms and their environment, involving biotic and abiotic factors, is ecology. An ecosystem is the result of this interaction, including processes like respiration and photosynthesis that exemplify the interdependence of biotic and abiotic components.

Explanation:

The interaction between living organisms and their environment, which includes both biotic and abiotic factors, is a fundamental aspect of biology and is referred to as ecology. Biotic factors are the living parts of the environment, while abiotic factors include the nonliving components such as temperature, water, soil, and air. The complex system formed by the interplay of these factors is known as an ecosystem. Within an ecosystem, living organisms carry out processes like respiration and photosynthesis that influence the abiotic conditions, while the physical processes in the environment can affect the behavior and the very existence of living organisms.

For example, plants, as biotic factors, require abiotic components like sunlight, water, and carbon dioxide to perform photosynthesis. This process not only enables plants to produce their own food but also contributes oxygen to the environment, benefiting other organisms. Another interaction would be animals breathing in oxygen (an abiotic factor) and exhaling carbon dioxide, which is then used by plants. These exchanges illustrate the interdependence of biotic and abiotic factors and the cyclical nature of ecosystem function.

As the peppered moth evolved over time, its wings changed from light to dark so that it could better A) find food to eat. B) combat pollution. C) hide from predators. D) withstand its climate.

Answers

Answer:

C) Hide from predators

Explanation:

The smoke would allow the peppered moths to be more visible

Therefore, they evolved into dark-peppered moths to be able to hide from those predators.

which of these describes the electrostatic force
a. particles of the same charge repel each other
b. particles of different masses repel each other
c. particles of opposite charge repel each other
d. particles without charge repel each other

Answers

Answer:

A

Explanation:

like charge repel, unlike attract

Answer:

A.

Explanation:

Particles of the same charge repel each other. E.g. + and + OR - and -.

Other Questions
During Jeffersons presidency, he dealt with the British and the Barbary pirates. Which do you think was the more difficult situation? Explain your reasoning. Compare each set of data. Determine which set shows greater variability.Set A5, 8, 9, 10, 12, 15, 16, 20Set B24, 34, 37, 42, 56, 57, 65 Which country most likely relies on primary economics activities Nefchio is a popular Web site among online gamers. It incorporates interactive and collaborative features to create a richer, more interesting, and more useful experience. In this scenario, Nefchio uses an approach called What are the following was an effect of brinkmanship seth painted the figure at the right on his wall how many square inches of paint did he use Which statement explains why typhoid is endemic in Southeast Asia?A. Many people are bitten by mosquitoes.B. Many people have unhealthy lifestyles. C. Many people do not have access to clean water.D. Many people do not have proper housing. _____ (They ask) cunto cuesta. Preguntan Piden Pregunten Pidan The diameter of a circle is 14 inches. Find the circumference.Use 22/7 or 3.14 for .Please show work! I will give brainliest! Malaya wrote a survey question in the newspaper about changing the school colors. Ninety percent of those who responded in an e-mail said they should be changed. She concludes that 90% of the student body wants the colors changed * Daphnia longicephala is a freshwater crustacean that can detect chemical cues produced by the predator Notonecta glauca. Researchers raised Daphnia clones and observed that those exposed to Notonecta chemical cues during their development produced larger protective crests. Crest height and width are measured as ratios to body length. The increase in the size of the crest width and height is not associated with a corresponding change to the Daphnias genome. Researchers hypothesize that growing a crest is energetically costly, so Daphnia does not develop the large crests in the absence of Notonecta.b. Explain how the presence of Notonecta chemical cues affects gene expression in the Daphnia. Directions: Closely read each of the four text passages provided in this document. Then, using evidence from at least three of the texts, write a well-developed argumentative essay regarding the given topic in the space below. Clearly establish your claim, distinguish your claim from alternate or opposing claims, and use specific, relevant, and sufficient evidence from at least three of the texts to develop your argument. Do not simply summarize each text. What is the rate of change and initial value for the linear relation that includes the points shown in the table? xy 23 45 67 89 Initial value: 1, rate of change: 2 Initial value: 1, rate of change: 1 Initial value: 2, rate of change: 2 Initial value: 3, rate of change: 2 HELP I NEED THIS ANSWER FAST! I WILL GIVE BRAINLIEST! I have a question about the 20,000 Leagues under the sea! - How do you know? What does Verne have his characters say and/or do that reveal that attitude?PLEASE HELP I NEED THIS AS FAST AS POSSIBLE! When pasting an object which has been copied from a different slide, where on the slide does the object paste, assuming nothing on the slide is selected?In the same location from where it was copiedWhere the user has clickedIn the first available placeholderIn the middle of the slide When a predator catches its prey, it may appear that the prey species suffers. But there are benefits to this type of interaction for prey species as well. What are two way in which the prey species might benefit from the predator hunting them? How did women contribute to the war effort in the north and south Of all the challenges and issues that the United States faces, which do you believe is the most serious in terms of foreign affairs and which in terms of domestic affairs? Choose one of each and write an essay that describes each issue and explains why you believe it is the most serious. Express the height of the tree in terms of trigonometric ratios.A) 50tan90B) 50sin90C) 90sin50D) 90tan50 Solve similar triangles (advanced) Steam Workshop Downloader