5. for the following measurements is expressed to three significant figures? a) 0.007 m b) 7077 mg c) 7.30 x 10^-7 km d) 0.070

Helppppppppppppppppppp me

masya89 [10]

The answer is A.
A pure substance is pure, so it cannot be separated in most cases.

8 0

4 years ago

How many elements are in Li2SO4?how many elements are in li2s 04 how many elements are in li2s 04

Free_Kalibri [48]

Answer:

3

Explanation:

the three elements involved in this compound are Li, S, O.

lithium, sulfur, and oxygen. Which create the ionic compound, "Lithium Sulfate."

7 atoms total, since there are two lithium, four oxygen, and one sulfate atom. this is a white inorganic salt.

6 0

3 years ago

4NH3 + 3O2 --> 2N2 + 6H2O

larisa86 [58]

The balanced reaction is:

4NH3 + 3O2 --> 2N2 + 6H2O

We are given the amount of reactants to be used for the reaction. This will be the starting point of our calculation.

83.7g of O2 ( 1 mol / 32 g) = 2.62 mol O2

2.81 moles of NH3

From the balanced reaction, we have a 4:3 ratio of the reactants. The limiting reactant would be oxygen. We will use the amount for oxygen for further calculations.

2.62 mol O2 (6 mol H2O / 3 mol O2) (18.02 g H2O / 1 mol H2O) = 94.42 g H2O

8 0

3 years ago

How would this change affect the food web?check all that apply

klio [65]

During the summer, when the land is brown and the grass is green, the population of mice decreases because mice are easily spotted by the organisms that eat them.

How would this change affect the food web? Check all that apply.

A. It will increase the grass population.

D. It will decrease the snake population

E. It will increase the grasshopper population

hope this helps! If so please mark brainliest and rate/heart to help my account if it did!!

7 0

3 years ago

When 50.0 mL of 1.27 M of HCl(aq) is combined with 50.0 mL of 1.32 M of NaOH(aq) in a coffee-cup calorimeter, the temperature of

sergij07 [2.7K]

Answer:

-55.9kJ/mol is the change in enthalpy of the reaction

Explanation:

In the reaction:

HCl(aq) + NaOH(aq) → H₂O(l) + NaCl

Some heat is released per mole of reaction.

To know how many moles reacts we need to find limiting reactant:

Moles HCl = 0.050L ₓ (1.27mol / L) = 0.0635 moles HCl

Moles NaOH = 0.050L ₓ (1.32mol / L) = 0.066 moles NaOH

As there are more moles of NaOH than moles of HCl, HCl is limiting reactant and moles of reaction are moles of limiting reactant, 0.0635 moles

Using the coffee-cup calorimeter equation we can find how many heat was released thus:

Q = C×m×ΔT

Where Q is heat released, C is specific heat of the solution (4.18J/g°C), m is mass of solution (100g because there are 100mL of solution -50.0mL of HCl and 50.0mL of NaOH- and density is 1g/mL) and ΔT is change in temperature (8.49°C)

Replacing:

Q = 4.18J/g°C×100g×8.49°C

Q = 3548.8J of heat are released in the reaction

Now, change in enthalpy, ΔH, is equal to change in heat (As is released heat ΔH < 0) per mole of reaction, that is:

ΔH = Heat / mol of reaction

ΔH = -3548.8J / 0.0635 moles of reaction

Negative because is released heat.

ΔH = -55887J / mol

ΔH =

<h3>-55.9kJ/mol is the change in enthalpy of the reaction</h3>

3 0

3 years ago