Muscles convert chemical energy into

During science class, while studying mixtures, you mix together table salt and sand. Your teacher challenges you to separate the

olga2289 [7]

The property to be used is sieving. you get a bowl and a sieve when you pour the sand and salt,the salt being the small particle sieve to the bowl while the sand remain on the sieve as residue

7 0

4 years ago

Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction: P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH

Pie

Answer: -1835 kJ

Explanation:

According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.

According to Hess’s law, the chemical equation can be treated as algebraic expressions and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.

$PCl_5(s)\rightarrow PCl_3(g)+Cl_2(g)$ $\Delta H_1=+157kJ$ (1)

$P_4(g)+6Cl_2\rightarrow 4PCl_3(g)$ $\Delta H_2=-1207J$ (2)

Net chemical equation:

$P_4(g)+10Cl_2(g)\rightarrow 4PCl_5(s)$ $\Delta H=?$ (3)

Multiplying equation (1) by 4, and reversing we get

$4PCl_3(g)+4Cl_2(g)\rightarrow 4PCl_5(s)$ $\Delta H_4=4\times -157kJ=-628kJ$ (4)

Adding (2) and (4)

$P_4(g)+10Cl_2(g)\rightarrow 4PCl_5(s)$ $\Delta H_3=\Delta H_2+\Delta H_4=-1207kJ-628kJ=-1835kJ$

Thus enthaply change for the reaction is -1835 kJ.

3 0

4 years ago

What is the sum of the coefficients needed to balance the combustion reaction of methane?

pishuonlain [190]

Answer: The sum of the coefficients needed to balance the combustion reaction of methane is 6.

Explanation:

Combustion is a chemical reaction in which hydrocarbons are burnt in the presence of oxygen to give carbon dioxide and water.

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

The chemical equation for combustion of methane will be :

$CH_4+2O_2\rightarrow CO_2+2H_2O$

The coefficient foer methane is 1 , 2 for oxygen , 1 for carbon dioxide and 2 for water. The sum is 6.

4 0

3 years ago

how do i word a formal letter to a teacher saying i didn't pay attention during the science lessons and i now have no idea what

Allushta [10]

Explanation:

Hello mr/mrs (name) I unfortunately couldn't pay attention to the class due to some issues I had therefore I don't know what we are doing in class

OR

Hello mr/mrs (name) I could understand what we were doing in class I would like it if you could break it down more or explain better to me

OR just say something it had something to do with your internet such as

Hello mr/mrs (name) I didn't understand what you were saying during our class due to some of my internet issues I was have throughout the day. I hope you can explain what we did during the class.

Those may be some of my excuses I've used before

they have worked for me:)

I don't know if that helped?:/

8 0

3 years ago

When a reaction occurs between atoms with ground state electron configuration 1s2 2s1 and 1s2 2s2 2p5 the predominant type of bo

fenix001 [56]

Answer: The bond formed between the elements will be ionic bond.

Explanation: We are given two elements having electronic configurations:

Element 1: $1s^22s^1$

Element 2: $1s^22s^22p^5$

Element 1 can easily loose 1 electron to attain stable electronic configuration and Element 2 can accept 1 electron to attain stable electronic configuration.

For these elements, there will be a complete transfer of electron from Element 1 to Element 2. Hence, this will form a ionic bond.

From the configuration, Element 1 is Lithium and Element 2 is Fluoride. So, the compound is LiF.

5 0

3 years ago