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2 years ago

4.

Chemistry

1 answer:

Nataly_w [17]2 years ago

6 0

Answer:

The current speed of Sarah is 8 m/s.

Explanation:

Speed:

''It is the distance travel in per unit time". It tells the capacity of moving object how fast it is moving.

Unit:

The system international unit of speed is m/s. It can also be given in Km/h

Formula:

r = d / t

r = speed (it can also be represented by v)

t = time taken to cover the distance

d = distance

Given data:

Distance = 400 m

Time = 50 s

Speed = ?

Solution:

v = d/ t

v = 400m / 50 s

v = 8 m/s

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What is the mass, in grams, of a pure gold cube that has a volume of 4.20cm^3 ?

Rama09 [41]

WOW, I gave you the answer, i used a periodic table, i got the mass of gold and i linked a helpful link my teacher gave me because we used it in a lab once.

5 0

3 years ago

NEED ANSWER ASAP! How many grams are in 1.50 moles of bromine liquid?

padilas [110]

Answer:

119.85 grams Br or 120. grams Br (sig figs)

Explanation:

1.50 moles Br 79.90 g Br

--------------------- x ------------------------ = 119.85 grams Br or 120 grams Br (sig figs)

1 mole

7 0

3 years ago

Which of the following reactions could be an elementary reaction? 2 NO2(g) + F2(g) → 2NO2F(g) Rate = k[NO2][F2] H2(g) + Br2(g) →

podryga [215]

Answer: The correct answer is $NO(g)+O_2(g)\rightarrow NO_2(g)+O(g);Rate=k[NO][O_2]$

Explanation:

Molecularity of the reaction is defined as the number of atoms, ions or molecules that must colloid with one another simultaneously so as to result into a chemical reaction.

Order of the reaction is defined as the sum of the concentration of terms on which the rate of the reaction actually depends. It is the sum of the exponents of the molar concentration in the rate law expression.

Elementary reactions are defined as the reactions for which the order of the reaction is same as its molecularity and order with respect to each reactant is equal to its stoichiometric coefficient as represented in the balanced chemical reaction.

For the given reactions:

Equation 1: $2NO_2(g)+F_2(g)\rightarrow 2NO_2F(g);Rate=k[NO_2][F_2]$

Molecularity of the reaction = 2 + 1 = 3

Order of the reaction = 1 + 1 = 2

This is not considered as an elementary reaction.

Equation 2: $H_2(g)+Br_2(g)\rightarrow 2HBr(g);Rate=k[H_2][Br_2]^{1/2}$

Molecularity of the reaction = 1 + 1 = 2

Order of the reaction = $1+\frac{1}{2}=\frac{3}{2}$

This is not considered as an elementary reaction.

Equation 3: $NO(g)+O_2(g)\rightarrow NO_2(g)+O(g);Rate=k[NO][O_2]$

Molecularity of the reaction = 1 + 1 = 2

Order of the reaction = 1 + 1 = 2

This is considered as an elementary reaction.

Equation 4: $NO_2(g)+CO(g)\rightarrow NO(g)+CO_2(g);Rate=k[NO_2]^2$

Molecularity of the reaction = 1 + 1 = 2

Order of the reaction = 2 + 0 = 2

In this equation, the order with respect to each reactant is not equal to its stoichiometric coefficient which is represented in the balanced chemical reaction. Hence, this is not considered as an elementary reaction.

Hence, the correct answer is $NO(g)+O_2(g)\rightarrow NO_2(g)+O(g);Rate=k[NO][O_2]$

3 0

3 years ago

( i need help on this one )

lara [203]

Answer:

1. False

2.True

Explanation:

7 0

3 years ago

Consider the following reaction: 2Mg(s)+O2(g)-->2MgO(s) delta H=-1204kJ

Pachacha [2.7K]

Answer:

a. The reaction is exothermic.

b. -87,9 kJ

c. 9,60g of Mg(s)

d. 602kJ are absorbed

Explanation:

Based on the reaction:

2Mg(s) + O₂(g) → 2MgO(s) ΔH = -1204kJ

a. The reaction is exothermic. Because ΔH<0. That means the reaction produces heat when occurs

b. 3,55g of Mg(s) are:

3,55g Mg × ( 1mol / 24,305g) = 0,146 moles of Mg(s)

As 2 moles of Mg(s) produce -1204 kJ of heat:

0,146 moles of Mg(s) × ( -1204kJ / 2mol Mg) = -87,9 kJ

c. If -238 kJ of heat were transferred. The moles of Mg(s) that react must be:

-238kJ × ( 2mol Mg / -1204kJ) = 0,395 moles of Mg(s). In grams:

0,395 moles × ( 24,305g / 1mol Mg) = 9,60g of Mg(s)

d. The reverse reaction is:

2MgO(s) → 2Mg(s) + O₂(g) ΔH = +1204kJ

40,5g of MgO(s) are:

40,5g MgO × ( 1mol MgO / 40,3044g) = 1,00 moles of MgO(s)

As 2 moles of MgO absorbe 1204kJ of energy:

1,00 moles of MgO(s) × ( +1204 kJ / 2mol MgO) = 602kJ are absorbed

I hope it helps!

7 0

3 years ago