How many significant figures are in the number 420,000 mi?

vazorg [7]

Answer:

See explanation

Explanation:

A double replacement reaction is a reaction where the atoms in the molecules replace each other to form two new molecules. However, if the products of the solution are soluble, then they could combine with the solution, and form a different set of products than expected.

Hope this helps!

3 0

2 years ago

what is the approximate ph at the equivalence point of a weak acid-strong base titration if 25 ml of aqueous formic acid require

vivado [14]

Answer:

pH at equivalence point is 8.52

Explanation:

$HCOOH+NaOH\rightarrow HCOO^{-}Na^{+}+H_{2}O$

1 mol of HCOOH reacts with 1 mol of NaOH to produce 1 mol of $HCOO^{-}$

So, moles of NaOH used to reach equivalence point equal to number of moles $HCOO^{-}$ produced at equivalence point.

As density of water is 1g/mL, therefore molarity is equal to molality of an aqueous solution.

So, moles of $HCOO^{-}$ produced = $\frac{29.80\times 0.3567}{1000}moles=0.01063moles$

Total volume of solution at equivalence point = (25+29.80) mL = 54.80 mL

So, at equivalence point concentration of $HCOO^{-}$ = $\frac{0.01063\times 1000}{54.80}M=0.1940M$

At equivalence point, pH depends upon hydrolysis of $HCOO^{-}$ . So, we have to construct an ICE table.

$HCOO^{-}+H_{2}O\rightleftharpoons HCOOH+OH^{-}$

I: 0.1940 0 0

C: -x +x +x

E: 0.1940-x x x

So, $\frac{[HCOOH][OH^{-}]}{[HCOO^{-}]}=K_{b}(HCOO^{-})=\frac{10^{-14}}{Ka(HCOOH)}$

species inside third bracket represent equilibrium concentrations

So, $\frac{x^{2}}{0.1940-x}=5.56\times 10^{-11}$

or, $x^{2}+(5.56\times 10^{-11}\times x)-(1.079\times 10^{-11})=0$

So, $x=\frac{-(5.56\times 10^{-11})+\sqrt{(5.56\times 10^{-11})^{2}+(4\times 1.079\times 10^{-11})}}{2}$

So, $x=3.285\times 10^{-6}M$

So, $pH=14-pOH=14+log[OH^{-}]=14+logx=14+log(3.285\times 10^{-6})=8.52$

5 0

2 years ago

if a 2.0g sample of water at 5.0celcius absorbs 21.8Joules of energy, the temprature of the sample will be raised by

Cerrena [4.2K]

You'd use the temperature change equation. The specific heat of water is always 4.18J/(g °C).
Equation to use: q=mCΔT

21.8=(2.0)(4.18)(Tf-5)
21.8=(8.36)(Tf-5)
21.8/8.36=Tf-5
2.61=Tf-5
2.61+5=Tf
Tf=7.61 °C

Since you want to know how many °C it raises, you wouldn't pay attention to the last 2 steps, however if you need to know the final temp, you want to go to the last step.

8 0

2 years ago

Which is a balanced chemical equation? A. C7H16 + 5O2 6CO2 + 4H2O B. C7H16 + 11O2 7CO2 + 8H2O C. C7H16 + 14O2 7CO2 +5H2O D. C7H1

nadya68 [22]

Answer:

$\boxed{\text{B.}}$

Explanation:

B.

$\rm C$_7$H_{16}$ + 11O$_2$ $\longrightarrow \,$ 7CO$_2$ + 8H$_2$O$

BALANCED. 7C, 16H, and 22O on each side of equation.

A.

$\rm C$_7$H$_{16}$ + 5O$_2$ $\longrightarrow \,\rm 6CO$_2$ + 4H$_2$O$

NOT BALANCED. 7C on left and 6C on right.

C.

$\rm C$_7$H$_{16}$ + 14O$_2$ $\longrightarrow \,$ 7CO$_2$ + 5H$_2$O$

NOT BALANCED. 16H on left and 10H on right.

D.

$\rm C$_7$H$_{16}$ + 22O$_2$ $\longrightarrow \, $ 14CO$_2$ + 16H$_2$O$

NOT BALANCED. 7C on left and 14C on right.

3 0

2 years ago

How are rare earth elements like neodymiun important to our technological world?

kherson [118]

Im assuming, if you find rare earth elements, it is important to the technological world bc you can make more products more better, and even invent new and more modern things.

7 0

2 years ago