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3 years ago

When a system performs work on the surroundings, the work is reported with a negative sign. True of False

1 answer:

5 0

The statement that is given above “When a system performs work on the surroundings, the work is reported with a negative sign” is true. When the surrounding performs work by the system, it is positive.

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A student observed a chemical reaction in which the mass of the products was measured to be less than the mass of the reactants.

nika2105 [10]

There chemical reactions that can realise or absorb gas to the atmosphere. This means it is harder or impossible to measure it with normal weighing devices and normal taring equipment. As a principal in chemical reactions we have conservation of mass.

5 0

3 years ago

According to the law of conservation of mass, what should the product side of this single replacement reaction look like? A. H2

Katyanochek1 [597]

Answer: The product side must be $ZnCl_2+H_2$

Explanation:

Single displacement reaction is defined as the reaction in which more reactive metal displaces a less reactive metal from its chemical reaction.

$AB+C\rightarrow CB+A$

Metal C is more reactive than metal A.

The reactivity of metal is determined by a series known as reactivity series. The metals lying above in the series are more reactive than the metals which lie below in the series.

Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form. This also means that total number of individual atoms on reactant side must be equal to the total number of individual atoms on the product side.

When zinc metal reacts with hydrochloric acid, it leads to the production of zinc chloride and hydrogen gas. The chemical reaction follows:

$Zn+2HCl\rightarrow ZnCl_2+H_2$

On reactant side:

Number of zinc atoms = 1

Number of hydrogen atoms = 2

Number of chlorine atoms = 2

On product side:

Number of zinc atoms = 1

Number of hydrogen atoms = 2

Number of chlorine atoms = 2

Hence, the product side must be $ZnCl_2+H_2$

8 0

3 years ago

A sample of food containing 27 g of fat, 48 g of carbohydrates and 20 g of protein is burned in a bomb calorimeter. In a perfect

rosijanka [135]

Answer:

38.3958 °C

Explanation:

As,

1 gram of carbohydrates on burning gives 4 kilocalories of energy

1 gram of protein on burning gives 4 kilocalories of energy

1 gram of fat on burning gives 9 kilocalories of energy

Thus,

27 g of fat on burning gives 9*27 = 243 kilocalories of energy

20 g of protein on burning gives 4*20 = 80 kilocalories of energy

48 gram of carbohydrates on burning gives 4*48 = 192 kilocalories of energy

Total energy = 515 kilocalories

Using,

$Q=m_{water}\times C_{water}\times (T_f-T_i)$

Given: Volume of water = 23 L = 23×10⁻³ m³

$Density=\frac{Mass}{Volume}$

Density of water= 1000 kg/m³

So, mass of the water:

$Mass\ of\ water=Density \times {Volume\ of\ water}$

$Mass\ of\ water=1000 kg/m^3 \times {0.023\ m^3}$

Mass of water = 23 kg

Initial temperature = 16°C

Specific heat of water = 0.9998 kcal/kg°C

$515=23\times 0.9998\times (T_f-16)$

Solving for final temperature as:

Final temperature = 38.3958 °C

8 0

3 years ago

What is the difference between the grassland and savanna biomes?

goblinko [34]

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.

Savanna are a mix of grasslands with some scattered trees in the area.
Grasslands are open grass fields.
They do not contain much trees as such.
The savanna and grasslands are renowned for their fauna diversity of beasts.

6 0

3 years ago

If 45.8 grams of potassium chlorate decomposes, how many grams of oxygen gas can be produced? 2KClO3 → 2KCl + 3O2

natta225 [31]

To do this problem, we must first look at the balanced chemical equation for the decomposition of potassium chlorate:

2KClO3 --> 2KCl + 3O2 

We can take the given amount of grams, and use the molar mass of KClO3 to convert to moles. Then, we can use the stoichiometric ratios to relate moles of KClO3 to moles of O2. 

(39.09)+(35.45)+(3*15.99)= 122.51 g/ mol = molar mass of KClO3 
45.8 g KClO3/ 122.51 g/ mol KClO3 = .374 moles KClO3 
.374 mol KClO3 *(3 moles O2/2 mol KClO3)= .560 moles O2 

Once we have moles of O2, we can convert to grams of O2. 

(2*15.99)= 31.98 g/mol = molar mass of O2 
(.560 moles O2) (31.98 g/mol)= 17.91 g O2 

Hope this helps :)

3 0

3 years ago